Endocrine Abstracts

Aim: The purpose of this study was to analysis BRAF V600E mutational status in papillary thyroid microcarcinomas (PTMCs) and unknown malignant potential thyroid tumors (UMP-TTs) and to investigate association of BRAF V600 positivity with clinicopathologic parameters.

Material and method: Seventy-two PTMC and 20 UMPTT tissues were included in this study. Genomic DNA was extracted from paraffin-embedded tumor tissue. The paraffin-embedded thyroid tumor samples were cut into 5 μm sections. The tumor areas dewaxed and dissected. DNA was isolated using QIAamp DNA-FFPE tissue kit. We amplified exon 15 of the BRAF gene, which contains the BRAF V600E mutation with RFLP analysis by using the following primers. The PCR products were electrophoresed in polyacrilamide gel. Samples were stained with silver nitrate and imaged.

Results: BRAF V600E mutation frequency in PTMCs was 41.6% (72/30), in unknown malignant potential well differentiated tumors (UMP WDT) was 80% (10/8). The BRAF V600E mutation was significantly associated with the classic variant of PTC 73.3% (P=0.047). BRAF positivitiy in PTMCs was significantly related to invasion of thyroid capsule 66.67% (P=0.003) and absence of the tumor capsule 80% (P=0.003). There was no significant correlation between the occurence of BRAF V600E mutation and advanced disease stages, extrathyroidal extension, cervical lymph node metastasis, age, gender, multifocality in PTMCs. The odd ratio for female sex in BRAF positive PTMCs was 2.46 for Hashimoto thyroiditis in BRAF positive PTMCs was 2.12.

Conclusion: BRAF V600E mutation was significantly associated with the classic variant, absence of the tumor capsule and penetration of the thyroid capcule in PTMCs. UMP-WDT lesions of the thyroid with BRAF mutation may represent PTC precursors or less aggressive type of PTCs. Tumor recurrence and poorer prognosis wasn’t associated with BRAF V600E mutation after a median follow-up of 22 months.