BRAF(V600E) mutation in anaplastic thyroid carcinomas and their accompanying differentiated carcinomas

Frequency of a BRAF(V600E) mutation in anaplastic thyroid carcinoma, which is thought to be derived mainly from papillary carcinoma by multi-step carcinogenesis, is much lower than that in papillary carcinomas. To clarify this phenomenon, we analysed BRAF(V600E) mutation in 20 cases of anaplastic carcinoma and 13 accompanying differentiated carcinomas. Among twenty cases of anaplastic carcinomas, nine and four accompanied papillary and follicular carcinomas, respectively. BRAF(V600E) mutation was found in four (20%) cases. BRAF(V600E) mutation was found in three of nine (33.3%), none of four and one of seven (14.3%) anaplastic carcinomas with papillary carcinoma, follicular carcinoma and without differentiated components, respectively. All three papillary carcinomas accompanied by anaplastic carcinoma with a BRAF(V600E) mutation were also shown to have a BRAF(V600E) mutation. In summary, BRAF(V600E) mutation was occasionally observed in anaplastic carcinomas with papillary carcinoma, and the low frequency of BRAF(V600E) mutation in anaplastic carcinoma was thought to be due to the low frequency of anaplastic carcinomas with papillary carcinoma. These findings raise a question about the classical model of anaplastic transformation and suggest some roles of thyroid cancer stem cells in the generation of anaplastic carcinoma.