RET PTC ONCOGENE ACTIVATION IS AN EARLY EVENT IN THYROID CARCINOGENESIS/

RET/PTC oncogene activation occurs in about 20% of human thyroid papil lary carcinomas, However, it is not known yet whether it is an early o r late event in the process of thyroid carcinogenesis, Here we demonst rate, by using a combined immunohistochemical and reverse-transcriptas e-polymerase chain reaction based approach, that RET/PTC activation is present in 11 out of 26 occult thyroid papillary carcinomas analysed. Therefore, we conclude that it represents an early event in the proce ss of thyroid cell transformation.