[TTF-1 expression and its diagnostic application in lung carcinomas]

To detect the expression of thyroid transcription factor 1 (TTF-1) and study its application in the diagnosis of lung carcinomas.

Of 134 specimens from lung lobectomy, 105 were primary lung carcinomas including 76 non-small cell carcinomas (NSCLCs), 28 small cell lung cancers (SCLCs) and 1 complex carcinoma (SCLC and SCC), and 29 were metastatic carcinomas. Expression of TTF-1 was detected by immunohistochemistry. The expression level of TTF-1 was graded as, +:6% to 25% of tumor cells positive, ++:26% to 50%, +++:51% to 75%, and ++++:> 76%.

The positive nuclear immunoreactivity of TTF-1 was identified in 23 of 28 SCLCs (82.1%), but none in squamous cell cancer (SCC) (P < 0.001). The positive expression rate of TTF-1 in lung adenocarcinomas (ACs) was 73.8% (31/42). There was no correlation between TTF-1 expression and ACs differentiation or ACs subtypes (P > 0.05). All but one (thyroid follicular carcinoma) metastatic ACs were TTF-1-positive. Mesenchymal component and lymphoid or inflammatory cells were consistently TTF-1-negative.

A significant difference of TTF-1 expression may assist in distinguishing SCLC from SCC, lymphoma or inflammatory lesions. Owing to its restrictive expression in lung tissue, TTF-1 might be used to differentiate primary from metastatic adenocarcinoma of the lung.