1. ¹Department of Laboratory Medicine, Osaka University Graduate School of Medicine, D2, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
2. ²Kuma Hospital, 8-2-35, Simoyamate-Dori, Chuo-Ku, Kobe, Hyogo 650-0011, Japan

Correspondence: Dr T Takano, E-mail: ttakano@labo.med.osaka-u.ac.jp

Revised 5 March 2007; Accepted 2 April 2007; Published online 24 April 2007.

Abstract

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.