The Relationship between the BRAF Mutations in Thyroid Papillary Carcinomas and the Prognostic Factors

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Background: Thyroid cancers account for about 1% of all human malignancies, with papillary thyroid carcinomas being the most common istotype. Several investigators have recently identified the most common BRAF mutation, the T1796A transversion mutation, in 29~69% of papillary thyroid cancers. The BRAF mutation has been demonstrated as a novel prognostic biomarker for the prediction of poor clinicopathological outcomes, such as increased incidence of extrathyroid invasion and distant metastasis of the tumor. In this study, we investigated the prevalence of the BRAF mutation of thyroid tissues obtained by a thyroidectomy, and its correlation with the clinicopathological outcomes. Methods: We studied 36 thyroid tissues obtained from 24 women and 12 men by thyroidectomies, including 30 papillary carcinomas, 3 follicular carcinomas, 1 medullary carcinoma and 2 nodular hyperplasia. The mutation was sought in all specimens using DNA sequencing. Results: We studied the BRAF exon 15 T1796A in these 36 thyroid tissue s. The mean age at surgery was 46.6, ranging from 18 to 72 years, with a median tumor size of 2.79, ranging from 1.5 to 4.5 cm. At the time of diagnosis, 27 of the 34 patients presented with some kind of extrathyroidal invasion of the tumor, and 16 had lymph node metastases. 16, 2 and 16 patients were in stages I, II and III, respectively. There was no distant metastasis. A missense mutation was found at T1796A in exon 15 in 21 of the 30 papillary carcinomas (70%). The other thyroid diseases, including the 3 follicular carcinomas, 1 medullary carcinoma and 2 nodular hyperplasia show no exon 15 T1759A transversion mutation. No statistically significant association was found between the BRAF mutations and clinicopathological characteristics of papillary carcinomas. Conclusion: The BRAF mutation is a important genetic alteration, with a high prevalence in papillary thyroid carcinomas. However, there was no significant association between the BRAF mutation and any of the clinicopathological factors. Further, large scale studies will be needed to evaluate the correlation between the BRAF mutation and the clinicopathological factors (J Kor Soc Endocrinol 20:224～229, 2005).