{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Thyroid transcription factor-1 (TTF-1) is a protein that regulates transcription of genes specific to the thyroid, lung and diencephalon. It is also known as thyroid-specific enhancer binding protein and NKX-2. It is used as a marker to determine if a tumor originates in the lung or thyroid. TTF-1 positive cells are found in Type II\n pneumocytes and Clara cells in the lung. In the thyroid, follicular and parafollicular cells are positive."}]},{"type":"paragraph","children":[{"type":"text","value":"TTF-1 is useful in differentiating primary Adenocarcinoma of the Lung from Metastatic Carcinomas of the breast and Malignant Mesothelioma. It can also be used to differentiate Small- Cell Lung Carcinoma from lymphoid infiltrates. For lung cancers, Adenocarcinomas are usually positive, while Squamous Cell Carcinomas\n and Large Cell Carcinomas are rarely positive. Small-Cell Carcinomas (of any primary site) are usually positive."}]}]}