The Frequency of BRAF Mutation in Very Small Papillary Thyroid Carcinomas

ABSTRACT

BACKGROUND: Papillary thyroid carcinoma (PTC) is the most common malignant tumor of the thyroid and BRAF (V600E) is the most frequent genetic alteration in PTCs. The aim of this study was to investigate the frequency of BRAF mutation, especially in very small PTCs. METHODS: We analyzed the presence of the BRAF mutation in PTCs in subgroups defined by tumor size (0.5 cm intervals). RESULTS: Of 140 patients, 85 (60.7%) showed a BRAF mutation. The frequency of BRAF mutation in the subgroup was 45/70 (64.3%) in tumors less than 0.5 cm in size, 18/28 (64.3%) in 0.6-1 cm tumors, 10/22 (45.5%) in 1.1-1.5 cm tumors, and 12/20 (60.0%) in 1.6-2 cm tumors. There was no statistically significant association between BRAF mutation and tumor size (p = 0.44). Similarly, BRAF mutation was not statistically related to age, sex, stage, perithyroidal extension or lymph node metastasis. On multivariate logistic regression analysis, tumor sizes larger than 0.5 cm were associated with lymph node metastasis (odds ratio, 3.79; 95% confidence interval, 1.81 to 7.91; p < 0.01). CONCLUSIONS: The BRAF mutation is not related to tumor size even in very small PTCs. The similar frequency of BRAF mutation in very small PTCs suggests that the BRAF mutation is a very early event in the tumorigenesis of PTCs.