TTF-1, cytokeratin 7, 34betaE12, and CD56/NCAM immunostaining in the subclassification of large cell carcinomas of the lung.

We selected a 4-stain immunopanel including thyroid transcription factor (7ITF)-], cytokeratin (CK)7, 34betaE12, and CD56/neural cell adhesion molecule(NCAM) to subclassify a series of 45 pulmonary large cell carcinomas (LCCs) on bronchial biopsy. All cases consisted of a large tumor cell proliferation with abundant cytoplasm, vesicular nuclei, and prominent nucleoli. Immunohistochemically, 27 tumors (60%)were subclassified as adenocarcinoma (7TF-1 +/CK7+,24; CK7+ only, 3), 10 (22%) as squamous cell carcinoma (34betaE12+ only), and 4 (9%) as LCC with neuroendocrine differentiation (CD56+, variably stained with TTF-I and CK7, 34betaE12-).