Test Details: Immunohistochemical testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. Thyroid transcription factor (TTF-1 also known as NKX2-1 or thyroid-specific enhancer-binding protein) is widely used as a specific and sensitive marker for the majority of bronchopulmonary adenocarcinomas and pulmonary small cell carcinoma in addition to follicular, papillary, and medullary thyroid carcinomas. A lesser degree of expression is found in large cell carcinoma of the lung, undifferentiated thyroid carcinoma, non-pulmonary small cell carcinoma of different locations, subset of extrahepatic cholangiocarcinomas, glial-ependymal and choroid plexus tumours, pituicytoma, granular cell tumour of the sellar region, meningeal tumours.