ANÁLISE MOLECULAR DA MUTAÇÃO V600E DO GENE BRAF EM MICROCARCINOMA PAPILAR DE TIREÓIDE

Abstract

Thyroid cancer is the commonest endocrine malignancy, with a rising incidence all over the world. This increasing incidence is almost exclusively due to the papillary thyroid cancer (PTC) and 30% to 50% of these tumors are papillary thyroid microcarcinomas (PTMC). The many score systems for risk stratification of these patients in low and high risk have been revealed to be unsatisfactory, leading to the search of a molecular marker wich could integrate a more reliable stratification system. BRAF V600E mutation is a frequent genetic event in the papillary thyroid carcinomas, that reflects its potential as a molecular marker in the PTMC. The aim of the present study was to evaluate the prevalence of such mutation in 80 paraffin embedded PTMC samples from the Pathology Department of the Hospital Araújo Jorge of Goiânia, Goiás, Brasil, obtained from patients operated between 1999 and 2006. Molecular analysis of the BRAF V600E mutation has been achieved by PCR and RFLP techniques. Statistical analysis included Chi-squared test with Yates s correction and Fisher s exact test. From the 80 cases of PTMC analysed, 73 (91.2%) were females, 47 patients (58.7%) were less than 45 years old and 33 (41.3%) were ≥ 45 years old. Lymph node metastasis were observed in 28 patients (35.0%) and extrathyroidal extension occurred in 19 cases (23.7%). Mutation BRAF V600E was observed in 50 cases (62.5%). There was no statistically significant association between clinicalpathologic parameters and the presence of the BRAFV600E. Our results showed that the BRAFV600E is a common genetic alteration in the PTMC, and it may represent an early event in the carcinogenesis of the thyroid gland. However, implications of this mutation in the prognostic of the PTMC were not observed.