Cytology is the gold standard method for the differential diagnosis of thyroid nodules, though 25–30% of them are classified as indeterminate. We aimed to set up a ‘thyroid risk score’ (TRS) to increase the diagnostic accuracy in these cases. We prospectively tested 135 indeterminate thyroid nodules. The pre-surgical TRS derived from the sum of the scores assigned at cytology, EU-TIRADS classification, nodule measurement, and molecular characterization, which was done by our PTC-MA assay, a customized array able to cost-effectively evaluate 24 different genetic alterations including point mutations and gene fusions. The risk of malignancy (ROM) increased paralleling the score: in the category >4 and ≤ 6 (low suspicion), >6 ≤ 8 (intermediate suspicion), and >8 (high suspicion); ROM was 10, 47 and 100%, respectively. ROC curves selected the score >6.5 as the best threshold to differentiate between malignant and benign nodules (P < 0.001). The TRS > 6.5 had a better performance than the single parameters evaluated separately, with an accuracy of 77 and 82% upon inclusion of noninvasive follicular thyroid neoplasm with papillary-like nuclear features among malignant or benign cases, respectively. In conclusion, for the first time, we generated a score combining a cost-effective molecular assay with already validated tools, harboring different specificities and sensitivities, for the differential diagnosis of indeterminate nodules. The combination of different parameters reduced the number of false negatives inherent to each classification system. The TRS > 6.5 was highly suggestive for malignancy and retained a high accuracy in the identification of patients to be submitted to surgery.

The incidence of papillary thyroid cancer (PTC) is rapidly growing, the recorded increase being mainly related to tumors ≤2 cm. The re-classification of tumors >1 and ≤2 cm limited to the thyroid from the T2 to the T1 category triggered some concerns about their best management. In order to identify possible predictors of disease outcome, several clinico-pathological features were analyzed by uni- and multivariate analyses in a retrospective consecutive series of 251 PTCs ≤2 cm. Moreover, since 37% of cases were submitted to prophylactic central compartment node dissection (CLND, VI–VII levels) and radioiodine ablation was performed only when the tumor had an extrathyroidal extension, the impact of these therapeutic tools on the final outcome was evaluated. Among all outcome predictors analyzed, only lymph node metastases and extracapsular invasion were strongly associated with persistence/recurrence. It is worth noting that neither age nor tumor size was a significant indicator of the outcome. Interestingly, as far as the therapeutic interventions are concerned, CLND was strongly associated with remission, whereas radioiodine ablation did not influence the outcome. In conclusion, present results confirm the prognostic influence of node metastases and extra-thyroidal invasion, indicating the need for aggressive treatment in tumors extending beyond the capsule. On the contrary, all pT1N0 tumors, regardless of the diameter, the number of intrathyroidal foci, and the age can be effectively treated only by surgery. The major impact of prophylactic CLND on prognosis suggests to routinely associate it to total thyroidectomy in cases with a preoperative diagnosis of malignancy.