Pheochromocytoma (PCC) and paraganglioma (PGL) are genetically and phenotypically heterogeneous catecholamine-producing neoplasms. They can occur sporadically or as a part of hereditary disease. Approximately 30% of PCC/PGL are believed to be caused by germline mutations (Welander et al. 2011). Of these, succinate dehydrogenase subunit B (SDHB) gene mutation is considered a high-risk factor for malignancy. Loss of heterozygosity at the SDHB locus (1p36) was observed in all tumors with SDHB mutation, and Gimenez-Roqueplo et al. (2003) strongly suggested that SDHB is a tumor suppressor gene. Subsequently, loss of SDHB protein immunoreactivity in SDHB-mutated PCC/PGL (SDHB–PCC/PGL) was reported with 100% sensitivity and 84% specificity (van Nederveen et al. 2009). Thus, SDHB immunohistochemistry can be used to screen SDHB–PCC/PGL using paraffin-embedded pathological materials. SDHB mutation is the only established factor that indicates future metastasis. Therefore, it is important to analyze the histological characteristics of SDHB–PCC/PGL.
It is generally accepted that it is difficult to distinguish histological differences between benign and malignant PCC/PGL. The current consensus is that a long-term follow-up is required after the surgery to screen for recurrence or metastasis in all PCC/PGL patients, regardless whether hereditary or sporadic in origin. Kimura et al. (2014) proposed a histological grading system called the Grading of Adrenal PCC and PGL (GAPP) classification for predicting metastasis. GAPP is composed of six factors: histological pattern, cellularity, presence or absence of comedo-type necrosis, vascular or capsular invasion, Ki67-labeling index (%), and elevated catecholamine type. Each factor was assigned a point and the number of points was summated. Tumor scores of 0–2, 3–6, and 7–10 were classified into well differentiated (WD), moderately differentiated (MD), and poorly differentiated (PD) types respectively. These types correlate with tumor metastasis and patient survival. Herein, we analyzed the clinicopathological features of patients with SDHB mutation using the GAPP classification and SDHB immunohistochemistry.
Fifteen Japanese patients with SDHB mutation and their tumors were examined. All patients were genetically tested and confirmed to have SDHB germline mutations. Patient clinical data, including age, gender, mutation sites, family history, elevated catecholamines (CA), metastasis, and present status after the initial surgical removal of the tumor, are summarized in Table 1. The same mutations were observed in SDHB exon 2 (c.137G>A) and SDHB exon 5 (c.470delT) in six and four patients respectively. Five of the patients (33%) had family history. The preoperative CA phenotypes of the patients included six norepinephrine plus dopamine, six norepinephrine only, and three nonfunctioning type. Eight of the patients (53%) had multiple distant metastases. Only two patients with multiple metastases died of the disease 37 and 12 years respectively after the initial surgery. The number of survival years from the first operation ranged from 2 to 37 years in eight patients; however, the remaining seven patients were operated upon within a past year and their prognosis could not be evaluated. Notably, four patients survived longer than 20 years with multiple metastases since the initial surgery (20, 25, 26, and 37 years respectively). Pathological data are summarized in Table 2. Nine tumors (60%) showed a pseudorosette pattern, which is histologically rare in ordinary PCC. Histological grading of the tumors was as follows: 1 WD, 13 MD (87%), and 1 PD.
SDHB gene mutations and clinical data of 15 patients
|Parameter||Mutation amino acid change||n|
|Mean age at diagnosis (years)||32.3±14.2 (17–61)|
|Exon/mutation cDNA nucleotide change||Exon 2/c.137G>A||R46Q||6|
|Intron4–5, exon5/c.424-7A>C; 424-6_427del||1|
|Family history of pheochromocytoma and paraganglioma||Positive||5 (33%)|
|Preoperative excessive catecholamine type||Norepinephrine+dopamine||6 (40%)|
|Present status||Died of disease||2|
|Alive with disease||5|
|Alive without disease||8|
Pathological data of pheochromocytomas and paragangliomas from 15 patients with SDHB mutation
|Tumor location||Adrenal gland||4 (27%)|
|With renal pelvis||1|
|Mediastinum with pelvic cavity||1|
|Tumor size (cm±S.D.)||6.35±2.74|
|Tumor metastasis||Presence||8 (53%)|
|Location of metastasis||Bone||3|
|Ovary and pelvic cavity||1|
|Omentum and peritoneum||1|
|Pseudorosette pattern||9 (60%)|
|GAPP score (mean±S.E.M.)||4.87±0.99|
|Histologic grade||Well differentiated||1|
|Moderately differentiated||13 (87%)|
In previous reports, genetic testing of SDHB revealed that the mutation sites were distributed throughout the entire gene (Benn et al. 2006). However, exons 2 and 5 appear to be the preferential mutation sites in the present study of Japanese patients. Patients with SDHB mutations were younger, had extra-adrenal tumors more frequently, and had shorter survival times (Amar et al. 2007). However, extraordinary long-term survivors with SDHB mutations and metastatic tumors have been reported. Young et al. (2002) reported a patient with SDHB mutation-associated familial malignant PGL with long survival, who was diagnosed with metastatic disease within 1 year after the initial presentation. The patient was well 30 years later, with little anti-tumor-specific therapy. Neumann et al. (2004) also reported two patients with malignant SDHB–PCC/PGL that had the disease longer than 20 and 32 years respectively. The present study includes four patients with long survival up to 37 years with multiple metastases since the initial surgery. The reasons for the extraordinarily long survival with multiple metastases are important and should be clarified. Timmers et al. (2007) reported that of the 29 patients with SDHB-PHEO/PGL, the catecholamine hypersecretion profile was norepinephrine plus dopamine in 13 patients (46%), norepinephrine only in 12 patients (41%), dopamine only in 1 patient (3%), and nonfunctioning in three patients (10%). Our present findings are similar to these data. Nonfunctioning PCC/PGL might reflect immature biochemical phenotypes. Dopamine hypersecretion and plasma methoxytyramine, the O-methylated metabolite of dopamine, have been considered as the features of immaturity and a marker for malignant PCC/PGL (Eisenhofer et al. 2012).
A pseudorosette pattern is a peculiar histology that is rarely observed in ordinary PCC/PGL. A pseudorosette pattern is sometimes observed in immature tumors of other organs, including pseudo-papillary tumors of the pancreas, some pituitary tumors, and ependymomas. It is surprising that the pseudorosette pattern was observed in nine (60%) of the 15 tumors in the present study. Thus, both catecholamine phenotype and tumor morphology revealed SDHB–PCC/PGL immaturity. Our histological analyses of SDHB–PCC/PGL revealed that most tumors (87%) are MD, whereas there is only one each of WD and PD tumor. Recent results from our Japanese nationwide survey of PCC/PGL have indicated that the 5-year survival rates were 100, 66.8, and 22.4% for the WD, MD, and PD types respectively (Kimura et al. 2014). Patients with MD type of SDHB–PCC/PGL may live for a long time after the initial surgery, even with multiple tumor metastases.
In conclusion, we would like to emphasize that the pseudorosette pattern in PCC/PGL and elevated norepinephrine plus dopamine or nonfunctioning are the features of SDHB mutations. Based on histopathology, the combination of SDHB-negative immunohistochemistry and the presence of pseudorosette pattern strongly suggest SDHB–PCC/PGL. Genomic analyses should be recommended for such cases.
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.
This study was supported by grants for a Research on Measures for Intractable Diseases, Research Committee on the Diagnosis and Treatment of Pheochromocytoma from the Ministry of Health, Labour, and Welfare of Japan (M Nakane) for Advancement for Hospital Function from the Japan Health, Labour, and Welfare Organization (N Kimura), and in part from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (grant number 21591168, K Takekoshi).
The authors thank K Terashima and T Moriyama for their dedication and cooperation in preparation of pathological materials.
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N Kimura and K Takekoshi contributed equally to this work