Endocrine Abstracts

Background: Thyroid nodules are prevalent in up to 60% of the adult population, occurring in a ratio of 4:1 woman/man. Using fine needle aspiration, approximately 25-30% of cases are categorized as "indeterminate": Bethesda 3 (B3) or Bethesda 4 (B4). In these cases, molecular tests, such as mir-THYpe full, can assist in diagnosis and prognosis, utilizing microRNA profiling and DNA analysis of mutations including BRAF V600E, pTERT C228T/C250T, RET M918T, C634Y/R, and V804L/M.

Objective: To evaluate by a retrospective analysis, the molecular profile data of Brazilian patients submitted to the mir-THYpe full test.

Methods: Molecular data from 3164 nodules (1812 B3 and 1352 B4) were analyzed, stratified by age (using a cut-off at 55 years), sex, mutation prevalence, and correlated with anatomopathological reports (APR) of patients who underwent surgery subsequent to the molecular test.

Results: Out of the total 3164 nodules, 64.2% (2032/3164) were classified negative and 35.8% (1132/3164) as positive for malignancy by mir-THYpe full test, being 75.5% (2389/3164) from female and 24.5% (775/3164) from men. In the negative results cohort, no mutations were detected, of which 20 patients underwent surgery and in 18 benign lesions were confirmed by APRs. In contrast, in the molecular positive results cohort, mutations were detected in 22.4% (254/1132) of the total cases, being: 232 BRAF V600E, 19 pTERT C228T, two RET M918T, and one RET C364R mutation. The pTERT C228T mutation was found in 5.2% (17/329) of the positive tests in individuals ≥55 years, compared to only 0.2% (2/803) in those <55 years (P < 0.0001). Regarding the BRAF V600E mutation, it was detected in 17.9% (59/329) of individuals ≥55 years, compared to 21.5% (173/803) in those <55 years (P = 0.17). Of all patients in the positive cohort, 207 APRs were accessible, confirming 127 cases of cancer/NIFTP.

Conclusion: In our cohort, many clinical parameters were aligned with what is found in other cohorts from other countries, like woman/man ratio, BRAF V600E mutation prevalence (including distribution by age or in all cohort) and prevalence of TERT C228T over C250T. Interestingly, the TERT positivity rate when divided by age showed an increased rate in the ≥55 years Brazilian patients with indeterminate cytology, suggesting acts as a risk factor for the occurrence of this mutation on indeterminate thyroid nodules.