Thyroid Transcription Factor-1, IHC with Interpretation [19278X]

This immunoassay is often used to evaluate neoplasms of unknown origin and assist in characterizing whether the neoplasm was derived from a pulmonary or thyroid lineage [1].

Thyroid transcription factor 1 (TTF-1) is a nuclear protein that is expressed in certain lung, thyroid, and diencephalon cells. Papillary, follicular, and medullary thyroid carcinomas are generally immunoreactive with TTF-1 antibodies. Approximately 75% of nonmucinous primary pulmonary adenocarcinomas and 90% of primary pulmonary small cell carcinomas are immunoreactive with TTF-1 antibodies. Primary pulmonary squamous cell carcinomas and mesotheliomas are generally non-reactive with TTF-1 antibodies. Likewise, dermal Merkel cell carcinomas are generally non-reactive with TTF-1 [1].

A small percentage of primary pulmonary squamous cell carcinomas stain positively with TTF-1. In addition, certain gynecologic tumors and small cell carcinomas of urothelial origin may express TTF-1 [1].

The results of this test should be interpreted in the context of pertinent clinical and family history as well as physical examination findings.

Reference
1. Rekhtman N, et al. Quick Reference Handbook for Surgical Pathologists. 2nd ed. Springer; 2019:3-37, 64, 79.