BRAFV600E mutation in papillary thyroid microcarcinoma: a meta-analysis

in Endocrine-Related Cancer
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  • 1 Department of Endocrinology, First Clinical Medical College, Jiangsu Institute of Nuclear Medicine, Department of Cardiology, Department of Neurology and Neuroscience, Departments of Nuclear Medicine, Ultrasound Medicine, Thyroid Institute, Division of Endocrinology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, 301 Yan Chang Middle Road, Shanghai 200072, China

The prognostic value of the BRAFV600E mutation, resulting in poor clinical outcomes of papillary thyroid carcinoma, has been generally confirmed. However, the association of BRAFV600E with aggressive clinical behaviors of papillary thyroid microcarcinoma (PTMC) has not been firmly established in individual studies. We performed this meta-analysis to examine the relationship between BRAFV600E mutation and the clinicopathological features of PTMC. We conducted a systematic search in PubMed, EMBASE, and the Cochrane library for relevant studies. We selected all the studies that reported clinicopathological features of PTMC patients with information available on BRAFV600E mutation status. Nineteen studies involving a total of 3437 patients met these selection criteria and were included in the analyses. The average prevalence of the BRAFV600E mutation was 47.48%, with no significant difference with respect to patient sex (male versus female) and age (younger than 45 years versus 45 years or older). Compared with the WT BRAF gene, the BRAFV600E mutation was associated with tumor multifocality (odds ratio (OR) 1.38; 95% CI, 1.04–1.82), extrathyroidal extension (OR 3.09; 95% CI, 2.24–4.26), lymph node metastases (OR 2.43; 95% CI, 1.28–4.60), and advanced stage (OR 2.39; 95% CI, 1.38–4.15) of PTMC. Thus, our findings from this large meta-analysis definitively demonstrate that BRAFV600E-mutation-positive PTMC are more likely to manifest with aggressive clinicopathological characteristics. In appropriate clinical settings, testing for the BRAFV600E mutation is likely to be useful in assisting the risk stratification and management of PTMC.

Abstract

The prognostic value of the BRAFV600E mutation, resulting in poor clinical outcomes of papillary thyroid carcinoma, has been generally confirmed. However, the association of BRAFV600E with aggressive clinical behaviors of papillary thyroid microcarcinoma (PTMC) has not been firmly established in individual studies. We performed this meta-analysis to examine the relationship between BRAFV600E mutation and the clinicopathological features of PTMC. We conducted a systematic search in PubMed, EMBASE, and the Cochrane library for relevant studies. We selected all the studies that reported clinicopathological features of PTMC patients with information available on BRAFV600E mutation status. Nineteen studies involving a total of 3437 patients met these selection criteria and were included in the analyses. The average prevalence of the BRAFV600E mutation was 47.48%, with no significant difference with respect to patient sex (male versus female) and age (younger than 45 years versus 45 years or older). Compared with the WT BRAF gene, the BRAFV600E mutation was associated with tumor multifocality (odds ratio (OR) 1.38; 95% CI, 1.04–1.82), extrathyroidal extension (OR 3.09; 95% CI, 2.24–4.26), lymph node metastases (OR 2.43; 95% CI, 1.28–4.60), and advanced stage (OR 2.39; 95% CI, 1.38–4.15) of PTMC. Thus, our findings from this large meta-analysis definitively demonstrate that BRAFV600E-mutation-positive PTMC are more likely to manifest with aggressive clinicopathological characteristics. In appropriate clinical settings, testing for the BRAFV600E mutation is likely to be useful in assisting the risk stratification and management of PTMC.

Introduction

A papillary thyroid carcinoma (PTC) measuring ≤1.0 cm or less in size is defined as papillary thyroid microcarcinoma (PTMC) by the World Health Organization Histological Classification of Tumors, and is often an incidental finding on histopathologic examination after thyroid surgery (LiVolsi et al. 2004). Owing to the widespread application of high-resolution thyroid ultrasound (US) and US-guided fine-needle aspiration biopsy (FNAB), PTC has been increasingly discovered at early stages in recent years. PTMC thus has become the most common form of PTC, accounting for almost half of all PTCs in large series reported in recent years (Davies & Welch 2006). According to the United States' Surveillance, Epidemiology, and End Results (SEER) data, the proportion of PTMC patients among all PTC cases has been rising rapidly since the 1980s; for example, it rose from 30% in 1988 to 40% in 2003 (Ries et al. 2007). The clinical management of patients with PTMCs, however, remains variable and controversial, because these tumors generally have a clinically indolent and innocuous course with excellent clinical prognosis. Some cases of PTMC, however, do exhibit aggressive clinicopathological characteristics and poor clinical outcomes (Roti et al. 2008). Therefore, identification of markers capable of distinguishing these aggressive tumors, especially in the phase before surgery, would be very useful in guiding appropriate clinical management of PTMC.

The BRAFV600E mutation, a point mutation at codon 600 of BRAF, results in substitution of valine to glutamate (V600E), leading to constitutive activation of the BRAF kinase and consequent uncontrolled activation of the MAPK pathway signaling (Davies et al. 2002). It is the most common genetic event in PTC and has been identified in about 45% of PTC cases and 25% of anaplastic thyroid cancer; but it does not occur in other thyroid cancers and benign tumors (Xing 2005, 2007). PTMCs have also been shown to harbor BRAFV600E mutations, which are considered to be the early stage of PTCs (de Biase et al. 2014). In recent years, the BRAFV600E mutation has emerged as a highly specific diagnostic marker and a useful prognostic factor in the risk stratification of PTC (Xing 2007). Results from many studies have indicated that BRAFV600E mutation is significantly associated with aggressive clinicopathological features of PTC, such as multifocality, extrathyroid extension, lymph node metastases (LNMs) at presentation, and advanced stage (Xing 2007, Mathur et al. 2010, Moses et al. 2010). Recent large meta-analyses of studies on general PTC re-confirmed the association of the BRAFV600E mutation with prognostic factors and poor clinical outcomes of PTCs (Kim et al. 2012, Tufano et al. 2012). However, the value of the BRAFV600E mutation as a prognostic marker in PTMC is not entirely clear, although PTMC also belongs to the well-differentiated papillary carcinoma group. Results from some individual studies indicated that BRAFV600E mutation was significantly correlated with more aggressive characteristics of PTMCs (Lupi et al. 2007, Lee et al. 2009, Lin et al. 2010, Kurtulmus et al. 2012), while others did not show such a relationship (Kim et al. 2005, Kwak et al. 2009, Choi et al. 2013). A major limitation of these latter studies is the limited numbers of patients with PTMC. Thus, additional studies including larger numbers of patients are needed to determine whether the presence of the BRAFV600E mutation is a prognostic factor for patients with PTMC. To this end, we performed a comprehensive meta-analysis on a large number of patients to further examine the relationship between the BRAFV600E mutation and the clinicopathological features of PTMC.

Materials and methods

Search strategy and selection criteria

We searched PubMed, EMBASE, and the Cochrane Library databases to identify all potential clinical studies published before January 2014 that reported on BRAFV600E and aggressive clinical behaviors of PTMC. The following search terms were employed: PTMC, thyroid microcarcinoma, papillary microcarcinoma of the thyroid, micropapillary thyroid cancer, papillary microcarcinoma, and BRAF. In addition to the primary electronic search, we also reviewed the related citations in PubMed and examined the references of retrieved articles for any relevant articles. We screened and selected pertinent articles for inclusion by using the software EndNote X6 (Thomson Reuters (Scientific), Inc., Midtown Manhattan, New York, NY, USA). Any studies that reported the clinicopathological features of PTMC patients with information available on BRAFV600E mutation status were considered for inclusion. If a study reported data on both PTMC and PTC >1.0 cm, only the former were used. The authors independently assessed articles for eligibility by screening all titles and abstracts and reviewing the full text of potentially relevant studies according to predefined inclusion and exclusion criteria. Any article was excluded i) if it only enrolled thyroid cancer subjects with tumor diameter >1.0 cm; ii) if it did not report any clinicopathological factors of the PTMC subjects (e.g., sex, age, multifocality, LNMs, extrathyroidal extension, and advanced stage); iii) if no BRAF mutation information was reported; iv) if it did not include PTMC defined by the WHO criteria; v) if only selected disease stages or only selected characteristics of PTMC were reported; and vi) if the study was published as an abstract, expert opinion, letter, conference article, editorial, case report, or review. When several papers were found analyzing the same population, only the most relevant was included. Only studies reported in English were included. Final selection of an eligible article was determined by consensus of the authors based on the above inclusion and exclusion criteria. Figure 1 summarizes the search strategy.

Figure 1
Figure 1

The search strategy.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Data extraction

We extracted the following information from each study: the first author, year of publication, country, number of participants, patient sex and age, clinicopathological features (including multifocality, LNMs, extrathyroidal extension, and tumor stages), BRAFV600E mutation status, BRAFV600E mutation sequencing method, and sample source.

Data analyses and statistical methods

Statistical analysis was conducted using Stata software version 12.0 (StataCorp., College Station, TX, USA). The occurrence of BRAFV600E was treated as a dichotomous variable and discrepancies between groups divided by clinicopathological factors were presented as odds ratios (ORs) with 95% CI, which were calculated using the Mantel–Haenszel method. Heterogeneity among the studies was tested using I2 statistics, which are a quantitative tool of variability across studies. An I2 value of 25, 50, and 75% indicates low, moderate, and high heterogeneity respectively (Higgins et al. 2003). We used a random effects model to synthesize the outcomes. To examine the robustness of the outcomes, we also performed sensitivity and subgroup analyses when heterogeneity was evident.

Results

The basic characteristics of the eligible studies are summarized in Table 1. Nineteen studies (Kim et al. 2005, Lupi et al. 2007, Rodolico et al. 2007, Frasca et al. 2008, Min et al. 2008, Kwak et al. 2009, Lee et al. 2009, Basolo et al. 2010, Jung et al. 2010, Lin et al. 2010, Kurtulmus et al. 2012, Marchetti et al. 2012, Schulten et al. 2012, Choi et al. 2013, Chung et al. 2013, Mussazhanova et al. 2013, Rossi et al. 2013, Virk et al. 2013, Zheng et al. 2013), including 3437 patients, fulfilled the eligibility criteria and were included in the meta-analysis. Overall, 1632 (47.48%) of these patients had BRAFV600E-mutation-positive PTMCs. Sample sizes of these studies ranged from 13 to 977 patients. The earliest study was published in November 2005 and the most recent study was published in July 2013. Not all of the studies had all of the variables of our interest and some studies contained variables not needed for this analysis. Therefore, for each study, we only analyzed data for the relevant variables. Virtually all of the included studies were retrospective studies. Four studies established BRAF status from FNAC materials, 11 studies from paraffin-embedded tissues, and the rest used a mixture of FNAC and paraffin-embedded tissues.

Table 1

Characteristics of the included studies

StudyCountryNo. of casesSex (F/M)Mean age (years)BRAFV600E mutation
SampleMethodNo. (%)
Kim et al. (2005)Korea6056/446.3±10.2FFPE tissuesSq31 (51.67)
Rodolico et al. (2007)USA214171/4341.3±9.9FFPE tissuesASA88 (41.12)
Lupi et al. (2007)aItaly230171/5946.1±12.7FFPE tissuesSSCP and Sq90 (39.13)
Min et al. (2008)Korea60NANAFFPE tissuesSSCP32 (53.33)
Frasca et al. (2008)Italy103NANAFFPE tissuesSq25 (24.27)
Lee et al. (2009)China6456/846.6±11.0FFPE tissue (n=40), fresh tissue (n=24)Sq24 (37.5)
Kwak et al. (2009)Korea339295/4445.4FNACSq213 (62.83)
Basolo et al. (2010)aItaly578435/143<45, 48.09%FFPE tissuesSSCP and Sq229 (39.62)
Jung et al. (2010)Korea147126/21<45, 39%FFPE tissuesSq110 (74.83)
Lin et al. (2010)China6152/949.0±12.4FNACSq21 (34.43)
Marchetti et al. (2012)Italy85NANAFNACSq63 (74.12)
Kurtulmus et al. (2012)Turkey64NA38.7±9.9FFPE tissuesFMCA19 (29.69)
Schulten et al. (2012)Saudi Arabia5648/836.4±13.5FFPE tissues, FNACSq10 (17.86)
Rossi et al. (2013)Italy50NANAFNACSq34 (68)
Choi et al. (2013)Korea10190/11<45, 24.75%FFPE tissuesSq72 (71.29)
Virk et al. (2013)bUSA124103/21NAFNAC (n=51), FFPE tissue (n=78)SSCP87 (70.16)
Mussazhanova et al. (2013)Japan1311/245.9±6.0FFPE tissuesSq6 (46.15)
Zheng et al. (2013)China977754/22345.95±10.5FFPE tissuesSq392 (40.12)
Chung et al. (2013)Korea11195/1647.9±13.6FNAC (n=85), FFPE tissues (n=26)Sq86 (77.48)
Total19 studies34371632 (47.48)

FFPE, formalin-fixed, paraffin-embedded; FNAC, fine-needle aspiration cytology; Sq, sequencing; SSCP, single-strand conformational polymorphism; FMCA, fluorescence melting curve analysis; ASA, allele-specific amplification; NA, not available.

In the two studies, the age at diagnosis of four patients from Lupi et al. (2007) and two patients from Basolo et al. (2010) was unknown.

BRAFV600E mutational analysis was performed in 129 tumors from 124 patients.

Sex

Eight studies (Kim et al. 2005, Kwak et al. 2009, Lee et al. 2009, Basolo et al. 2010, Choi et al. 2013, Mussazhanova et al. 2013, Virk et al. 2013, Zheng et al. 2013), involving 456 male and 1800 female patients, were analyzed for the association between BRAFV600E mutation and patient sex. BRAFV600E mutation was detected in 235 (51.54%) of the 456 male and 819 (45.50%) of the 1800 female PTMC patients. No significant association was found between sex and BRAFV600E mutation (Fig. 2; OR 1.36; 95% CI, 0.98–1.90). The heterogeneity among the studies was low (I2=30.6%).

Figure 2
Figure 2

Random effect model of the odds ratios (ORs) with 95% CI of the frequency of BRAFV600E mutation associated with sex is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Age

To assess the relationship between BRAFV600E mutation and age, patients were divided into two groups based on age, one younger than 45 years and the other 45 years or older. Six studies were available for this analysis (Kim et al. 2005, Lupi et al. 2007, Basolo et al. 2010, Choi et al. 2013, Mussazhanova et al. 2013, Zheng et al. 2013), involving 1953 patients. Of the 1071 patients of 45 years age or older, 423 (39.50%) were BRAFV600E-mutation-positive, and 394 (44.67%) of the 882 patients younger than 45 years were BRAFV600E-mutation-positive. The association between BRAFV600E and patient age is close to significance (Fig. 3; OR 0.78; 95% CI, 0.60–1.00). The heterogeneity among the studies was low (I2=28.4%).

Figure 3
Figure 3

Random effect model of the odds ratios (ORs) with 95% CI of the frequency of BRAFV600E mutation associated with age is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Thyroid multifocality

Ten studies (Kim et al. 2005, Lupi et al. 2007, Frasca et al. 2008, Kwak et al. 2009, Basolo et al. 2010, Lin et al. 2010, Kurtulmus et al. 2012, Marchetti et al. 2012, Choi et al. 2013, Zheng et al. 2013), including 2598 patients, were analyzed for the association between BRAFV600E mutation and multifocality of PTMC. Of 1155 patients with BRAFV600E, 406 (35.15%) had multifocal disease, whereas 448 (31.05%) of the 1443 patients with WT BRAFV600E had multifocal disease. A significant association existed between the BRAFV600E mutation and multifocality (Fig. 4; OR 1.38; 95% CI, 1.04–1.82). The heterogeneity of the data was not significant and the I2 estimate of the variance between the studies was 45.4%.

Figure 4
Figure 4

Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with thyroid multifocality is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Extrathyroidal extension

Twelve studies (Kim et al. 2005, Lupi et al. 2007, Frasca et al. 2008, Lee et al. 2009, Basolo et al. 2010, Lin et al. 2010, Kurtulmus et al. 2012, Marchetti et al. 2012, Choi et al. 2013, Mussazhanova et al. 2013, Rossi et al. 2013, Zheng et al. 2013) involving 1006 patients with BRAFV600E and 1380 patients with WT BRAF were analyzed with regard to extrathyroidal extension. Extrathyroidal extension was detected in 393 (39.07%) of the 1006 patients with BRAFV600E, and was detected in 213 (15.43%) of the 1380 patients with WT BRAF. There was a significant association between BRAFV600E mutation and extrathyroidal extension (Fig. 5; OR 3.09; 95% CI, 2.24–4.26). No significant statistical heterogeneity was found among the studies (I2=36.3%).

Figure 5
Figure 5

Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with extrathyroidal extension is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Lymph node metastasis

Seventeen studies (Kim et al. 2005, Lupi et al. 2007, Rodolico et al. 2007, Frasca et al. 2008, Min et al. 2008, Lee et al. 2009, Basolo et al. 2010, Jung et al. 2010, Lin et al. 2010, Kurtulmus et al. 2012, Marchetti et al. 2012, Choi et al. 2013, Chung et al. 2013, Mussazhanova et al. 2013, Rossi et al. 2013, Virk et al. 2013, Zheng et al. 2013) including 1385 cases with BRAFV600E and 1620 patients with WT BRAF were analyzed with regard to LNM. LNM was found in 486 (35.09%) of 1385 cases with BRAFV600E and in 171 (10.56%) of 1620 patients with WT BRAF. There was a significant association between BRAFV600E mutation and LNM (Fig. 6; OR 2.43; 95% CI, 1.28–4.60). Significant statistical heterogeneity was found among the studies (I2=85.8%). Sensitivity analysis was performed and, as a result, the heterogeneity of the data markedly decreased to 41.3% when the study of Zheng et al. (2013) was excluded. We did not find any other major changes when sensitivity analysis was performed in other cases. Therefore, this study was a major contribution to the heterogeneity. With this treatment, a significant association still existed between BRAFV600E mutation and LNM after exclusion of this study (OR 1.94; 95% CI, 1.35–2.79).

Figure 6
Figure 6

Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with lymph node metastasis is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Advanced stages

Nine studies (Kim et al. 2005, Frasca et al. 2008, Kwak et al. 2009, Lee et al. 2009, Basolo et al. 2010, Lin et al. 2010, Schulten et al. 2012, Choi et al. 2013, Zheng et al. 2013) including 1017 patients with BRAFV600E and 1320 patients with WT BRAF were analyzed with regard to advanced stage of PTMC. Advanced stage (defined as TNM III/IV) was found in 356 (35.00%) of the 1017 patients with mutant BRAF and in 213 (16.14%) of the 1320 patients with WT BRAF. There was a significant association between BRAFV600E and advanced stage (Fig. 7; OR 2.39; 95% CI, 1.38–4.15). Significant heterogeneity was found among the studies (I2=77.7%).

Figure 7
Figure 7

Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with the advanced stage (TNM III/IV) is shown.

Citation: Endocrine-Related Cancer 22, 2; 10.1530/ERC-14-0531

Analyses of the effects of BRAFV600E mutation on the aggressive clinicopathological features of PTMC according to country

Subgroup analysis was conducted according to the country of the study subjects to investigate the potential sources of heterogeneity and assess whether the effects of BRAFV600E on aggressive clinicopathological features of PTMC were associated with geographic regions (Table 2). The effect estimates were broadly consistent among the subgroups that were analyzed. The heterogeneity was significantly decreased in the subgroup analysis of extra-thyroidal extension and advanced stage. However, the results of the subgroup analyses also indicated that BRAFV600E is not significantly associated with high-risk tumor features (e.g., extra-thyroidal extension, LNM, and advanced stage) of PTMC in patients from Korea, where the prevalence of the BRAFV600E mutation was unusually high. It is also notable that the Korean subgroup has a significant odds ratio for tumor multimodality, while the other geographical subgroups do not.

Table 2

Subgroup analyses of the effects of BRAFV600E mutation on the aggressive clinicopathological features of PTMC according to country

SubgroupTotal no. of patientsOR (95% CI)I2 (%)
Multifocality
 Korea (three studies)5001.54 (1.02–2.32)0
 Italy (four studies)9961.26 (0.84–1.90)34.8
 China (two studies)10381.78 (0.42–7.55)81.7
 Turkey (one study)642.75 (0.91–8.27)0
Extrathyroidal extension
 Korea (two studies)1611.09 (0.56–2.12)0
 Italy (five studies)10463.64 (2.59–5.12)0
 China (three studies)11023.97 (2.46–6.40)19.7
 Others (two studies)772.90 (0.70–12.00)0
Lymph node metastasis
 Korea (five studies)4791.18 (0.67–2.08)43.4
 Italy (five studies)10462.65 (1.56–4.50)6.5
 China (three studies)11025.52 (1.02–29.91)91.2
 USA (two studies)3012.24 (1.23–4.11)0
 Others (two studies)772.08 (0.23–18.79)52.7
Advanced stage
 Korea (three studies)5000.97 (0.66–1.43)0
 China (three studies)11023.98 (2.48–6.37)20.7
 Italy (two studies)6794.09 (2.34–7.17)0
 Saudi Arabia (one study)562.44 (0.20, 29.94)0

Discussion

In recent decades, the incidence of thyroid cancer, especially that of PTMC, has been rapidly rising (Davies & Welch 2006). In the United States, it has been reported that PTMC is the most common thyroid malignancy in patients older than the age of 45 years (Hughes et al. 2011). Therefore, it has become a major challenge to appropriately manage the increasing number of PTMC cases. PTMCs seem to consist of two biologically distinct subpopulations: a population with indolent tumors that have minimal or no potential for progression and a second population that has more aggressive behaviors and poor prognosis (Guerra et al. 2012a). Currently, for low-risk PTMC cases which are often incidentally detected by imaging studies, such as ultrasound screening, limited treatment with appropriate clinical monitoring without aggressive interventions is considered to be a reasonable therapeutic strategy (Ito & Miyauchi 2007, 2009). However, this strategy is not applicable to patients with high-risk characteristics, such as those with extrathyroidal extension, LNM, advanced stages and distant metastasis because these factors are usually associated with aggressive cancer and a poor prognosis (Ito & Miyauchi 2007, 2009). Both European Thyroid Association (Pacini et al. 2006) and American Thyroid Association guidelines (Cooper et al. 2009) recommended hemithyroidectomy for PTMCs in the absence of preoperative evidence of LNM. Unfortunately, it is often not a straightforward task to identify preoperative LNM in PTMCs because of the limitations associated with ultrasonographic examinations, which diminish the detection sensitivities. Thus, LNM is frequently found during an operation or in the pathology postoperatively, with an incidence reported to be 30–65% (Guerra et al. 2012a). As in PTC in general, LNM is also associated with tumor recurrence of PTMC as demonstrated in a large meta-analysis (Roti et al. 2008). In order to decrease the overall recurrence rate and possibly improve the survival rate, it would be reasonable to remove metastatic lymph nodes in the neck, which is the most common source of recurrence of PTMC. Thus, if known preoperatively to be associated with LNM, it would be reasonable to treat PTMC with total or near-total thyroidectomy with the appropriate extent of central neck dissection. On the other hand, indiscriminative prophylactic central compartment neck dissection is associated with significant risks of surgical complications such as the damage to the recurrent laryngeal nerve and hypoparathyroidism (Brown et al. 2008, Witt 2008) and should be avoided. Therefore, identification of aggressive PTMC preoperatively and design of appropriate treatments have become an important yet often challenging issue.

BRAFV600E has provided the promise of better and practically helpful risk stratification for PTC, including PTMC, which can be applied as a prognostic molecular marker for preoperative testing of FNAB specimens (Xing et al. 2009, Joo et al. 2012). Several molecular mechanisms are well known to underly the aggressive role of BRAFV600E. It has been widely demonstrated that the BRAFV600E mutation can promote upregulation of many tumor-promoting genes and downregulation of tumor suppressor genes and aberrant silencing of thyroid iodide-handling genes, impairing the sensitivity of PTC to radioactive iodine treatment (Liu et al. 2007, Xing 2013). These results all indicate that, biologically, the BRAFV600E mutation plays a critical role in the tumorigenesis, progression, and aggressiveness of PTC. This explains well the role of the BRAFV600E mutation in the increased risk of aggressiveness of PTMC positive for this mutation. Given the heterogeneity of BRAF mutation in PTC as indicated by the results of studies by the Vitale group (Guerra et al. 2012a,b) and the recent elegant de Biase study (de Biase et al. 2014), multifocal PTMC lesions may not necessarily harbor BRAF mutations.

As the utility of BRAFV600E mutation assessment in the management of PTC has been increasingly appreciated (Xing 2007, 2013, Kim et al. 2012, Xing et al. 2013a), mutational analysis may also be useful in the preoperative management of patients with PTMC. In this meta-analysis, we found a strongly significant association of BRAFV600E mutation with extrathyroidal invasion, multifocality, LNM, and advanced disease stages of PTMC, confirming that the presence of BRAFV600E is a risk for increased aggressiveness of PTMC. Therefore, BRAFV600E may be a useful prognostic molecular marker to help identify PTMCs with increased risk of aggressive clinicopathological behaviors, including LNM and hence increased risk of disease recurrence. Xing et al. (2013b) carried out a study of 1849 patients to investigate the association between BRAFV600E and PTC-related mortality and found that the BRAFV600E mutation was significantly associated with increased cancer-related mortality among patients with PTC compared with the WT BRAF group. Many studies on PTC have also demonstrated a strong association between the BRAFV600E mutation and tumor recurrence (e.g., Xing et al. 2005, 2014, Elisei et al. 2012). There have been few studies that have assessed the relationship between patient survival or tumor recurrence of PTMC and the BRAFV600E mutation, and no reliable conclusions could be reached due to the relatively small number of cases in most studies. Subgroup analyses in two recent large multicenter studies demonstrated a significant association of the BRAFV600E mutation with tumor recurrence and patient mortality in PTMC (Xing et al. 2013b, 2014). However, larger studies could be even more helpful to definitively address the role of BRAFV600E in tumor recurrence and patient mortality of PTMC.

Although cancer-related mortality rate among patients with PTMC is extremely low, recurrence is relatively common and occurs in 4.0–13.4% of patients (Davies et al. 2002, Ross et al. 2009, Joo et al. 2012, Tufano et al. 2012), which is associated with an increase of fivefold in the risk of cancer-related death (Liu et al. 2007). Therefore, Xing (2009) suggested that the primary management goal for this cancer is to prevent its progression and to identify, prevent, and manage its recurrence. To this end, more aggressive treatment of BRAF-mutation-positive PTMC in appropriate clinical settings may be reasonable. This seems to be the case particularly in areas where the prevalence of BRAFV600E was low. In contrast, BRAFV600E may have relatively limited prognostic utility in areas, such as Korea, where the BRAFV600E mutation has an extremely high prevalence (Jung et al. 2010, Choi et al. 2013, Chung et al. 2013).

Conclusion

In conclusion, the results of this large meta-analysis demonstrate that the BRAFV600E mutation is strongly associated with aggressive clinicopathologic behaviors of PTMC, including extrathyroidal extension, LNM, and advanced stage. The BRAFV600E mutation may prove to be a useful prognostic molecular marker in assisting the risk stratification and management of PTMC in appropriately defined clinical settings.

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding

This work was supported by Chinese Medical Society Clinical grant numbers 12020550355 and 13020260411 and the Chinese National Science Foundation grant number 81472579.

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  • Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F & Schlumberger M 2009 Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 19 11671214. (doi:10.1089/thy.2009.0110).

    • Search Google Scholar
    • Export Citation
  • Davies L & Welch HG 2006 Increasing incidence of thyroid cancer in the United States, 1973–2002. Journal of the American Medical Association 295 21642167. (doi:10.1001/jama.295.18.2164).

    • Search Google Scholar
    • Export Citation
  • Davies H, Bignell GR, Cox C, Stephens P, Edkins S, Clegg S, Teague J, Woffendin H, Garnett MJ & Bottomley W 2002 Mutations of the BRAF gene in human cancer. Nature 417 949954. (doi:10.1038/nature00766).

    • Search Google Scholar
    • Export Citation
  • Elisei R, Viola D, Torregrossa L, Giannini R, Romei C, Ugolini C, Molinaro E, Agate L, Biagini A & Lupi C 2012 The BRAF V600E mutation is an independent, poor prognostic factor for the outcome of patients with low-risk intrathyroid papillary thyroid carcinoma: single-institution results from a large cohort study. Journal of Clinical Endocrinology and Metabolism 97 43904398. (doi:10.1210/jc.2012-1775).

    • Search Google Scholar
    • Export Citation
  • Frasca F, Nucera C, Pellegriti G, Gangemi P, Attard M, Stella M, Loda M, Vella V, Giordano C & Trimarchi F 2008 BRAF V600E mutation and the biology. Endocrine-Related Cancer 15 191205. (doi:10.1677/ERC-07-0212).

    • Search Google Scholar
    • Export Citation
  • Guerra A, Fugazzola L, Marotta V, Cirillo M, Rossi S, Cirello V, Forno I, Moccia T, Budillon A & Vitale M 2012a A high percentage of BRAF V600E alleles in papillary thyroid carcinoma predicts a poorer outcome. Journal of Clinical Endocrinology and Metabolism 97 23332340. (doi:10.1210/jc.2011-3106).

    • Search Google Scholar
    • Export Citation
  • Guerra A, Sapio MR, Marotta V, Campanile E, Rossi S, Forno I, Fugazzola L, Budillon A, Moccia T & Fenzi G 2012b The primary occurrence of BRAF V600E is a rare clonal event in papillary thyroid carcinoma. Journal of Clinical Endocrinology and Metabolism 97 517524. (doi:10.1210/jc.2011-0618).

    • Search Google Scholar
    • Export Citation
  • Higgins JP, Thompson SG, Deeks JJ & Altman DG 2003 Measuring inconsistency in meta-analyses. BMJ 327 557560. (doi:10.1136/bmj.327.7414.557).

  • Hughes DT, Haymart MR, Miller BS, Gauger PG & Doherty GM 2011 The most commonly occurring papillary thyroid cancer in the United States is now a microcarcinoma in a patient older than 45 years. Thyroid 21 231236. (doi:10.1089/thy.2010.0137).

    • Search Google Scholar
    • Export Citation
  • Ito Y & Miyauchi A 2007 A therapeutic strategy for incidentally detected papillary microcarcinoma of the thyroid. Nature Clinical Practice. Endocrinology & Metabolism 3 240248. (doi:10.1038/ncpendmet0428).

    • Search Google Scholar
    • Export Citation
  • Ito Y & Miyauchi A 2009 Prognostic factors and therapeutic strategies for differentiated carcinomas of the thyroid. Endocrine Journal 56 177192. (doi:10.1507/endocrj.K08E-166).

    • Search Google Scholar
    • Export Citation
  • Joo JY, Park JY, Yoon YH, Choi B, Kim JM, Jo YS, Shong M & Koo BS 2012 Prediction of occult central lymph node metastasis in papillary thyroid carcinoma by preoperative BRAF analysis using fine-needle aspiration biopsy: a prospective study. Journal of Clinical Endocrinology and Metabolism 97 39964003. (doi:10.1210/jc.2012-2444).

    • Search Google Scholar
    • Export Citation
  • Jung CK, Kang YG, Bae JS, Lim DJ, Choi YJ & Lee KY 2010 Unique patterns of tumor growth related with the risk of lymph node metastasis in papillary thyroid carcinoma. Modern Pathology 23 12011208. (doi:10.1038/modpathol.2010.116).

    • Search Google Scholar
    • Export Citation
  • Kim TY, Kim WB, Song JY, Rhee YS, Gong G, Cho YM, Kim SY, Kim SC, Hong SJ & Shong YK 2005 The BRAF V600E mutation is not associated with poor prognostic factors in Korean patients with conventional papillary thyroid microcarcinoma. Clinical Endocrinology 63 588593. (doi:10.1111/j.1365-2265.2005.02389.x).

    • Search Google Scholar
    • Export Citation
  • Kim TH, Park YJ, Lim JA, Ahn HY, Lee EK, Lee YJ, Kim KW, Hahn SK, Youn YK & Kim KH 2012 The association of the BRAF V600E mutation with prognostic factors and poor clinical outcome in papillary thyroid cancer: a meta-analysis. Cancer 118 17641773. (doi:10.1002/cncr.26500).

    • Search Google Scholar
    • Export Citation
  • Kurtulmus N, Duren M, Ince U, Cengiz Yakicier M, Peker O, Aydin O, Altiok E, Giray S & Azizlerli H 2012 BRAFV600E mutation in Turkish patients with papillary thyroid cancer: strong correlation with indicators of tumor aggressiveness. Endocrine 42 404410. (doi:10.1007/s12020-012-9651-x).

    • Search Google Scholar
    • Export Citation
  • Kwak JY, Kim EK, Chung WY, Moon HJ, Kim MJ & Choi JR 2009 Association of BRAFV600E mutation with poor clinical prognostic factors and US features in Korean patients with papillary thyroid microcarcinoma. Radiology 253 854860. (doi:10.1148/radiol.2533090471).

    • Search Google Scholar
    • Export Citation
  • Lee X, Gao M, Ji Y, Yu Y, Feng Y, Li Y, Zhang Y, Cheng W & Zhao W 2009 Analysis of differential BRAFV600E mutational status in high aggressive papillary thyroid microcarcinoma. Annals of Surgical Oncology 16 240245. (doi:10.1245/s10434-008-0233-3).

    • Search Google Scholar
    • Export Citation
  • Lin KL, Wang OC, Zhang XH, Dai XX, Hu XQ & Qu JM 2010 The BRAF mutation is predictive of aggressive clinicopathological characteristics in papillary thyroid microcarcinoma. Annals of Surgical Oncology 17 32943300. (doi:10.1245/s10434-010-1129-6).

    • Search Google Scholar
    • Export Citation
  • Liu D, Liu Z, Condouris S & Xing M 2007 BRAF V600E maintains proliferation, transformation, and tumorigenicity of BRAF-mutant papillary thyroid cancer cells. Journal of Clinical Endocrinology and Metabolism 92 22642271. (doi:10.1210/jc.2006-1613).

    • Search Google Scholar
    • Export Citation
  • LiVolsi VA, Albores-Saavedra J, Asa SL, Baloch ZW, Sobrinho-Simőes M, Wenig B. 2004 Papillary carcinoma. In: Pathology and Genetics of Tumours of Endocrine Organs. World Health Organization Classification of Tumours, vol 8, pp 57–66. Eds RA DeLellis, RV Lloyd, PU Heitz & C Eng. Lyon, France: IARC Press

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    • Search Google Scholar
    • Export Citation
  • Marchetti I, Iervasi G, Mazzanti CM, Lessi F, Tomei S, Naccarato AG, Aretini P, Alberti B, Di Coscio G & Bevilacqua G 2012 Detection of the BRAF V600E mutation in fine needle aspiration cytology of thyroid papillary microcarcinoma cells selected by manual macrodissection: an easy tool to improve the preoperative diagnosis. Thyroid 22 292298. (doi:10.1089/thy.2011.0107).

    • Search Google Scholar
    • Export Citation
  • Mathur A, Weng J, Moses W, Steinberg SM, Rahbari R, Kitano M, Khanafshar E, Ljung BM, Duh QY & Clark OH 2010 A prospective study evaluating the accuracy of using combined clinical factors and candidate diagnostic markers to refine the accuracy of thyroid fine needle aspiration biopsy. Surgery 148 11701176.discussion 1176–1177 (doi:10.1016/j.surg.2010.09.025).

    • Search Google Scholar
    • Export Citation
  • Min HS, Choe G, Kim SW, Park YJ, Park do J, Youn YK, Park SH, Cho BY & Park SY 2008 S100A4 expression is associated with lymph node metastasis in papillary microcarcinoma of the thyroid. Modern Pathology 21 748755. (doi:10.1038/modpathol.2008.51).

    • Search Google Scholar
    • Export Citation
  • Moses W, Weng J, Sansano I, Peng M, Khanafshar E, Ljung BM, Duh QY, Clark OH & Kebebew E 2010 Molecular testing for somatic mutations improves the accuracy of thyroid fine-needle aspiration biopsy. World Journal of Surgery 34 25892594. (doi:10.1007/s00268-010-0720-0).

    • Search Google Scholar
    • Export Citation
  • Mussazhanova Z, Matsuda K, Naruke Y, Mitsutake N, Stanojevic B, Rougounovitch T, Saenko V, Suzuki K, Nishihara E & Hirokawa M 2013 Significance of p53-binding protein 1 (53BP1) expression in thyroid papillary microcarcinoma: association with BRAF V600E mutation status. Histopathology 63 726734. (doi:10.1111/his.12233).

    • Search Google Scholar
    • Export Citation
  • Pacini F, Schlumberger M, Dralle H, Elisei R, Smit JW, Wiersinga W & European Thyroid Cancer Taskforce 2006 European consensus for the management of patients with differentiated thyroid carcinoma of the follicular epithelium. European Journal of Endocrinology 154 787803. (doi:10.1530/eje.1.02158).

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*

(F Li and G Chen contributed equally to this work and should be considered co-first authors)

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  • View in gallery

    The search strategy.

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    Random effect model of the odds ratios (ORs) with 95% CI of the frequency of BRAFV600E mutation associated with sex is shown.

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    Random effect model of the odds ratios (ORs) with 95% CI of the frequency of BRAFV600E mutation associated with age is shown.

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    Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with thyroid multifocality is shown.

  • View in gallery

    Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with extrathyroidal extension is shown.

  • View in gallery

    Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with lymph node metastasis is shown.

  • View in gallery

    Random effect model of the odds ratios (ORs) with 95% CI of the BRAFV600E mutation associated with the advanced stage (TNM III/IV) is shown.

  • Basolo F, Torregrossa L, Giannini R, Miccoli M, Lupi C, Sensi E, Berti P, Elisei R, Vitti P & Baggiani A 2010 Correlation between the BRAF V600E mutation and tumor invasiveness in papillary thyroid carcinomas smaller than 20 millimeters: analysis of 1060 cases. Journal of Clinical Endocrinology and Metabolism 95 41974205. (doi:10.1210/jc.2010-0337).

    • Search Google Scholar
    • Export Citation
  • de Biase D, Cesari V, Visani M, Casadei GP, Cremonini N, Gandolfi G, Sancisi V, Ragazzi M, Pession A & Ciarrocchi A 2014 High-sensitivity BRAF mutation analysis: BRAF V600E is acquired early during tumor development but is heterogeneously distributed in a subset of papillary thyroid carcinomas. Journal of Clinical Endocrinology and Metabolism 99 E1530E1538. (doi:10.1210/jc.2013-4389).

    • Search Google Scholar
    • Export Citation
  • Brown AP, Chen J, Hitchcock YJ, Szabo A, Shrieve DC & Tward JD 2008 The risk of second primary malignancies up to three decades after the treatment of differentiated thyroid cancer. Journal of Clinical Endocrinology and Metabolism 93 504515. (doi:10.1210/jc.2007-1154).

    • Search Google Scholar
    • Export Citation
  • Choi SY, Park H, Kang MK, Lee DK, Lee KD, Lee HS, Kim SW, Lee EN & Hong JC 2013 The relationship between the BRAFV600E mutation in papillary thyroid microcarcinoma and clinicopathologic factors. World Journal of Surgical Oncology 11 291. (doi:10.1186/1477-7819-11-291).

    • Search Google Scholar
    • Export Citation
  • Chung SY, Lee JS, Lee H, Park SH, Kim SJ & Ryu HS 2013 Cytomorphological factors and BRAF mutation predicting risk of lymph node metastasis in preoperative liquid-based fine needle aspirations of papillary thyroid carcinoma. Acta Cytologica 57 252258. (doi:10.1159/000343617).

    • Search Google Scholar
    • Export Citation
  • Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F & Schlumberger M 2009 Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 19 11671214. (doi:10.1089/thy.2009.0110).

    • Search Google Scholar
    • Export Citation
  • Davies L & Welch HG 2006 Increasing incidence of thyroid cancer in the United States, 1973–2002. Journal of the American Medical Association 295 21642167. (doi:10.1001/jama.295.18.2164).

    • Search Google Scholar
    • Export Citation
  • Davies H, Bignell GR, Cox C, Stephens P, Edkins S, Clegg S, Teague J, Woffendin H, Garnett MJ & Bottomley W 2002 Mutations of the BRAF gene in human cancer. Nature 417 949954. (doi:10.1038/nature00766).

    • Search Google Scholar
    • Export Citation
  • Elisei R, Viola D, Torregrossa L, Giannini R, Romei C, Ugolini C, Molinaro E, Agate L, Biagini A & Lupi C 2012 The BRAF V600E mutation is an independent, poor prognostic factor for the outcome of patients with low-risk intrathyroid papillary thyroid carcinoma: single-institution results from a large cohort study. Journal of Clinical Endocrinology and Metabolism 97 43904398. (doi:10.1210/jc.2012-1775).

    • Search Google Scholar
    • Export Citation
  • Frasca F, Nucera C, Pellegriti G, Gangemi P, Attard M, Stella M, Loda M, Vella V, Giordano C & Trimarchi F 2008 BRAF V600E mutation and the biology. Endocrine-Related Cancer 15 191205. (doi:10.1677/ERC-07-0212).

    • Search Google Scholar
    • Export Citation
  • Guerra A, Fugazzola L, Marotta V, Cirillo M, Rossi S, Cirello V, Forno I, Moccia T, Budillon A & Vitale M 2012a A high percentage of BRAF V600E alleles in papillary thyroid carcinoma predicts a poorer outcome. Journal of Clinical Endocrinology and Metabolism 97 23332340. (doi:10.1210/jc.2011-3106).

    • Search Google Scholar
    • Export Citation
  • Guerra A, Sapio MR, Marotta V, Campanile E, Rossi S, Forno I, Fugazzola L, Budillon A, Moccia T & Fenzi G 2012b The primary occurrence of BRAF V600E is a rare clonal event in papillary thyroid carcinoma. Journal of Clinical Endocrinology and Metabolism 97 517524. (doi:10.1210/jc.2011-0618).

    • Search Google Scholar
    • Export Citation
  • Higgins JP, Thompson SG, Deeks JJ & Altman DG 2003 Measuring inconsistency in meta-analyses. BMJ 327 557560. (doi:10.1136/bmj.327.7414.557).

  • Hughes DT, Haymart MR, Miller BS, Gauger PG & Doherty GM 2011 The most commonly occurring papillary thyroid cancer in the United States is now a microcarcinoma in a patient older than 45 years. Thyroid 21 231236. (doi:10.1089/thy.2010.0137).

    • Search Google Scholar
    • Export Citation
  • Ito Y & Miyauchi A 2007 A therapeutic strategy for incidentally detected papillary microcarcinoma of the thyroid. Nature Clinical Practice. Endocrinology & Metabolism 3 240248. (doi:10.1038/ncpendmet0428).

    • Search Google Scholar
    • Export Citation
  • Ito Y & Miyauchi A 2009 Prognostic factors and therapeutic strategies for differentiated carcinomas of the thyroid. Endocrine Journal 56 177192. (doi:10.1507/endocrj.K08E-166).

    • Search Google Scholar
    • Export Citation
  • Joo JY, Park JY, Yoon YH, Choi B, Kim JM, Jo YS, Shong M & Koo BS 2012 Prediction of occult central lymph node metastasis in papillary thyroid carcinoma by preoperative BRAF analysis using fine-needle aspiration biopsy: a prospective study. Journal of Clinical Endocrinology and Metabolism 97 39964003. (doi:10.1210/jc.2012-2444).

    • Search Google Scholar
    • Export Citation
  • Jung CK, Kang YG, Bae JS, Lim DJ, Choi YJ & Lee KY 2010 Unique patterns of tumor growth related with the risk of lymph node metastasis in papillary thyroid carcinoma. Modern Pathology 23 12011208. (doi:10.1038/modpathol.2010.116).

    • Search Google Scholar
    • Export Citation
  • Kim TY, Kim WB, Song JY, Rhee YS, Gong G, Cho YM, Kim SY, Kim SC, Hong SJ & Shong YK 2005 The BRAF V600E mutation is not associated with poor prognostic factors in Korean patients with conventional papillary thyroid microcarcinoma. Clinical Endocrinology 63 588593. (doi:10.1111/j.1365-2265.2005.02389.x).

    • Search Google Scholar
    • Export Citation
  • Kim TH, Park YJ, Lim JA, Ahn HY, Lee EK, Lee YJ, Kim KW, Hahn SK, Youn YK & Kim KH 2012 The association of the BRAF V600E mutation with prognostic factors and poor clinical outcome in papillary thyroid cancer: a meta-analysis. Cancer 118 17641773. (doi:10.1002/cncr.26500).

    • Search Google Scholar
    • Export Citation
  • Kurtulmus N, Duren M, Ince U, Cengiz Yakicier M, Peker O, Aydin O, Altiok E, Giray S & Azizlerli H 2012 BRAFV600E mutation in Turkish patients with papillary thyroid cancer: strong correlation with indicators of tumor aggressiveness. Endocrine 42 404410. (doi:10.1007/s12020-012-9651-x).

    • Search Google Scholar
    • Export Citation
  • Kwak JY, Kim EK, Chung WY, Moon HJ, Kim MJ & Choi JR 2009 Association of BRAFV600E mutation with poor clinical prognostic factors and US features in Korean patients with papillary thyroid microcarcinoma. Radiology 253 854860. (doi:10.1148/radiol.2533090471).

    • Search Google Scholar
    • Export Citation
  • Lee X, Gao M, Ji Y, Yu Y, Feng Y, Li Y, Zhang Y, Cheng W & Zhao W 2009 Analysis of differential BRAFV600E mutational status in high aggressive papillary thyroid microcarcinoma. Annals of Surgical Oncology 16 240245. (doi:10.1245/s10434-008-0233-3).

    • Search Google Scholar
    • Export Citation
  • Lin KL, Wang OC, Zhang XH, Dai XX, Hu XQ & Qu JM 2010 The BRAF mutation is predictive of aggressive clinicopathological characteristics in papillary thyroid microcarcinoma. Annals of Surgical Oncology 17 32943300. (doi:10.1245/s10434-010-1129-6).

    • Search Google Scholar
    • Export Citation
  • Liu D, Liu Z, Condouris S & Xing M 2007 BRAF V600E maintains proliferation, transformation, and tumorigenicity of BRAF-mutant papillary thyroid cancer cells. Journal of Clinical Endocrinology and Metabolism 92 22642271. (doi:10.1210/jc.2006-1613).

    • Search Google Scholar
    • Export Citation
  • LiVolsi VA, Albores-Saavedra J, Asa SL, Baloch ZW, Sobrinho-Simőes M, Wenig B. 2004 Papillary carcinoma. In: Pathology and Genetics of Tumours of Endocrine Organs. World Health Organization Classification of Tumours, vol 8, pp 57–66. Eds RA DeLellis, RV Lloyd, PU Heitz & C Eng. Lyon, France: IARC Press

  • Lupi C, Giannini R, Ugolini C, Proietti A, Berti P, Minuto M, Materazzi G, Elisei R, Santoro M & Miccoli P 2007 Association of BRAF V600E mutation with poor clinicopathological outcomes in 500 consecutive cases of papillary thyroid carcinoma. Journal of Clinical Endocrinology and Metabolism 92 40854090. (doi:10.1210/jc.2007-1179).

    • Search Google Scholar
    • Export Citation
  • Marchetti I, Iervasi G, Mazzanti CM, Lessi F, Tomei S, Naccarato AG, Aretini P, Alberti B, Di Coscio G & Bevilacqua G 2012 Detection of the BRAF V600E mutation in fine needle aspiration cytology of thyroid papillary microcarcinoma cells selected by manual macrodissection: an easy tool to improve the preoperative diagnosis. Thyroid 22 292298. (doi:10.1089/thy.2011.0107).

    • Search Google Scholar
    • Export Citation
  • Mathur A, Weng J, Moses W, Steinberg SM, Rahbari R, Kitano M, Khanafshar E, Ljung BM, Duh QY & Clark OH 2010 A prospective study evaluating the accuracy of using combined clinical factors and candidate diagnostic markers to refine the accuracy of thyroid fine needle aspiration biopsy. Surgery 148 11701176.discussion 1176–1177 (doi:10.1016/j.surg.2010.09.025).

    • Search Google Scholar
    • Export Citation
  • Min HS, Choe G, Kim SW, Park YJ, Park do J, Youn YK, Park SH, Cho BY & Park SY 2008 S100A4 expression is associated with lymph node metastasis in papillary microcarcinoma of the thyroid. Modern Pathology 21 748755. (doi:10.1038/modpathol.2008.51).

    • Search Google Scholar
    • Export Citation
  • Moses W, Weng J, Sansano I, Peng M, Khanafshar E, Ljung BM, Duh QY, Clark OH & Kebebew E 2010 Molecular testing for somatic mutations improves the accuracy of thyroid fine-needle aspiration biopsy. World Journal of Surgery 34 25892594. (doi:10.1007/s00268-010-0720-0).

    • Search Google Scholar
    • Export Citation
  • Mussazhanova Z, Matsuda K, Naruke Y, Mitsutake N, Stanojevic B, Rougounovitch T, Saenko V, Suzuki K, Nishihara E & Hirokawa M 2013 Significance of p53-binding protein 1 (53BP1) expression in thyroid papillary microcarcinoma: association with BRAF V600E mutation status. Histopathology 63 726734. (doi:10.1111/his.12233).

    • Search Google Scholar
    • Export Citation
  • Pacini F, Schlumberger M, Dralle H, Elisei R, Smit JW, Wiersinga W & European Thyroid Cancer Taskforce 2006 European consensus for the management of patients with differentiated thyroid carcinoma of the follicular epithelium. European Journal of Endocrinology 154 787803. (doi:10.1530/eje.1.02158).

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