The diagnosis of thyroid carcinoma in pleural fluid can be particularly challenging as thyroid transcription factor -1 (TTF-1) which is a marker for carcinoma of thyroid origin is also positive in lung adenocarcinomas (which are more frequently associated with pleural effusions) and thyroglobulin (TG) can often be negative in poorly differentiated/analplastic thyroid carcinomas.
Thyroid transcription factor-1 amplification and expressions in lung adenocarcinoma tissues and pleural effusions predict patient survival and prognosis.
As a molecular marker of detecting pleural micrometastasis, TTF-1 mRNA may be helpful to diagnose the cancer cells in PEs of patients with lung cancer, especially with PPA.