immunohistochemical lung cancers
- related: lung mass and cancer
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Immunohistochemical characterization of lung cancers. CK20 is positive in most adenocarcinomas of the large and small intestines, stomach, pancreas, and bile ducts, as well as mucinous tumors of the ovary. Abbreviations: SCC, squamous cell carcinoma; SCLC, small cell lung cancer; CK, cytokeratin; TTF, thryoid transcription factor.1
Immunohistochemistry analysis has become an important tool in interpreting the origin of metastatic cancers. Thyroid transcription factor-1 is positive in the large majority of lung adenocarcinomas (>87%). Cytokeratin (CK)7 positivity and Napsin-A positivity (+ in 80%) also point to lung adenocarcinoma as the tumor site of origin. The negative CK20 and positive CK7 point against a colon primary. The mildly elevated carcinoembryonic antigen is consistent with levels seen in active smokers.
Lung squamous cell carcinoma is usually p40, p63 (+ in >98%), and CK5/6 (+ in >93%) positive and often CK7 negative. The more common epithelioid variant of malignant mesothelioma can at times be confused with adenocarcinoma, and although this patient is at risk for mesothelioma because of his occupation as a brake liner, the negative calretinin and CK5/6, and the positive thyroid transcription factor-1, point against mesothelioma and in favor of lung adenocarcinoma (choice D is incorrect).1
