Expression of S100A2 and S100A6 in thyroid carcinomas.

Aims:  S100 calcium-binding proteins are known to play multiple roles in carcinoma development. In this study, we focused on two kinds of these proteins, S100A2 and S100A6, and investigated their expression in thyroid neoplasms. Methods and results:  We investigated S100A2 and S100A6 expression in 141 thyroid neoplasms by immunohistochemistry. S100A2 was not expressed in normal follicles or follicular tumours, with one exception. Although 89.5% of papillary carcinoma were positive for S100A2, the expression was heterogeneous except in two cases. In anaplastic carcinoma, 78.5% of cases expressed S100A2 diffusely, while the remaining cases were negative. In normal follicles, S100A6 expression was always low, while 8.3% of follicular adenomas and 39.5% of follicular carcinomas showed increased expression. In papillary carcinomas, S100A6 expression was increased in 75% of cases, but in anaplastic carcinomas it was decreased, with only 14.3% showing high expression. Conclusions:  The expression patterns of S100A2 and S100A6 in thyroid neoplasms are unique compared with those of other carcinomas, suggesting that: (i) S100A2 and S100A6 contribute to certain events in papillary carcinoma progression, and (ii) S100A2 expression is one of the biological characteristics of anaplastic carcinoma.