[TTF-1: neither angel nor demon].

Expressed in thyroid, lung and diencephalon, the Thyroid transcription factor-1 (TTF-1) regulates, in these organs, the transcription of specific genes. This review focuses on the use of TTF-1 as a diagnostic tool in thyroid and lung carcinomas. According to the literature, TTF-1 seems to be involved in aggressive relapses. In some cases it could be also involved in the remission. The use of TTF-1 as a prognostic tool for some neoplasms is discussed.