Usefulness of Cdx2 in separating mucinous bronchioloalveolar adenocarcinoma of the lung from metastatic mucinous colorectal adenocarcinoma.

We studied the diagnostic value of Cdx2 to distinguish mucinous bronchioloalveolar carcinoma from mucinous colorectal adenocarcinoma metastatic to the lung. We retrieved 92 via the hospital computer system, including 30 mucinous bronchioloalveolar carcinomas, 32 nonmucinous bronchioloalveolar carcinomas, and 30 mucinous colorectal adenocarcinomas metastatic to the lung. All cases were confirmed by clinical history and surgical resection with occasional immunohistochemical studies. Cases were stained with antibodies against Cdx2, thyroid transcription factor-1 (TTF-1), cytokeratin (CK) 7, and CK20. Bronchioloalveolar carcinoma, mucinous type, showed positive staining for Cdx2, TTF-1, CK7, and CK20 in 0 (0%), 5 (17%), 30 (100%), and 18 (60%) of 30 cases, respectively; nonmucinous tumors were positive in 0 (0%), 30 (94%), 32 (100%), and 0 (0%) of 32 cases, respectively. For colorectal adenocarcinoma, the positive staining for Cdx-2, TTF-1, CK7, and CK20 was 29 (97%), 0 (0%), 7 (23%), and 29 (97%) of 30 cases, respectively. Our results demonstrated Cdx2 as a sensitive and specific marker for differentiating metastatic colorectal adenocarcinoma from mucinous bronchioloalveolar adenocarcinoma.