Thyroid transcription factor-1
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Thyroid transcription factor-1 (TTF-1) is a protein that regulates transcription of genes specific for the thyroid, lung, and diencephalon. It is also known as thyroid specific enhancer binding protein. It is used in anatomic pathology as a marker to determine if a tumor arises from the lung or thyroid.
TTF-1 positive cells are found in type II pneumocytes and Clara cells in the lung. In the thyroid, follicular and parafollicular cells are positive.
For lung cancers, adenocarcinomas are usually positive, while squamous cell carcinomas and large cell carcinomas are rarely positive. Small cell carcinomas (of any primary site) are usually positive.