KRT7 and lung adenocarcinoma: The mean age of diagnosis is at 62.3 years.3 Some risk factors associated with sarcomatoid carcinoma of the lung include smoking tobacco products and exposure to asbestos in building construction and electrical insulation.6 Pan-cytokeratin (CAM 5.2 and LP 34) has been reported to be present in sarcomatoid carcinoma of the lung.7 Staining with CK7 and CK20 antibodies can help discriminate between primary lung adenocarcinoma and adenocarcinoma from a different organ that has metastasized to the lung.