PRIMARY VERSUS METASTATIC PULMONARY ADENOCARCINOMA - AN IMMUNOHISTOCHEMICAL STUDY USING VILLIN AND CYTOKERATIN-7 AND CYTOKERATIN-20

In an attempt to identify a specific immunohistochemical profile that would distinguish primary pulmonary adenocarcinoma from metastatic ade nocarcinomas, we studied paraffin-embedded sections of 133 primary (65 lung, 22 colon, 19 breast, 17 clear renal cell, and 10 endometrium) a nd nine metastatic (five colon, one breast, two clear renal cell, and one endometrium) adenocarcinomas to the lung with monoclonal antibodie s to cytokeratin (CK) 7, CK 20, and villin. Primary pulmonary adenocar cinomas revealed a unique immunohistochemical profile of CK7 + (98%)/C K20 - (86%)/villin + (68%). This pattern of coordinate expression was not observed in any other type of adenocarcinoma. Colonic tumors were CK7 - (85%)/ CK20 + (96%)/villin + (96%). Most of the villin-positive colonic carcinomas displayed a robust brush-border staining pattern. N one of the other tumors reacted to villin with a brush-border pattern. The breast and endometrial adenocarcinomas revealed an essentially si milar profile of CK7 +/CK20 -/villin-. In general, clear rena-cell car cinomas were nonreactive to all three markers. We conclude that the ob served differences in CK7, CK20, and villin immunohistochemical profil es may prove diagnostically helpful in cases of adenocarcinoma of unkn own origin.