Pulmonary metastases of colonic carcinoma. Distinction from pulmonary adenocarcinoma.

Pulmonary metastases may develop in patients with colonic carcinoma. Histopathologic separation of a solitary colonic metastasis from a primary pulmonary adenocarcinoma may be problematic. With the use of a polyclonal antibody to carcinoembryonic antigen, a monoclonal antibody to cytokeratin (CAM 5.2), and a monoclonal carcinoembryonic antigen antibody (D-14), we compared 23 colonic carcinomas metastatic to the lung with 24 primary pulmonary adenocarcinomas. Both carcinomas manifested similar histologic features. However, foci of "dirty necrosis" were common in all but one of the colonic neoplasms, and foci were observed in only four of the primary lung carcinomas. The polyclonal carcinoembryonic antigen antibody did not distinguish metastatic colonic carcinoma from primary pulmonary adenocarcinoma. All colonic tumors stained with D-14, while three primary pulmonary adenocarcinomas stained diffusely, and eight stained focally. Staining with D-14 will not absolutely distinguish colonic from pulmonary adenocarcinoma. However, positive D-14 staining and the presence of dirty necrosis should identify most colonic carcinomas. True-negative D-14 staining practically excludes a colonic origin.