Immunohistochemical detection of cluster 1 small cell lung cancer antigen and chromogranin A in lung carcinomas.

Eighteen small cell lung cancers (SCLCs), 108 non-SCLCs (67 adenocarcinomas, 29 squamous cell carcinomas and 12 large cell carcinomas) were immunohistochemically examined for expressions of cluster 1 SCLC antigen/N-CAM and chromogranin A with monoclonal antibodies NCC-Lu-243 and anti-chromogranin A. The cell membranes of all the SCLCs and three of the 67 adenocarcinomas (4.5%) were stained for cluster 1 SCLC antigen/N-CAM. Eight of the 18 SCLCs (44.4%), and three of the 67 adenocarcinomas (4.5%) were stained for chromogranin A, but no squamous cell carcinoma or large cell carcinoma was stained for both antigens. Two of the three adenocarcinomas which expressed cluster 1 SCLC antigen/N-CAM had been suspected of being either SCLC or poorly-differentiated adenocarcinoma cytologically, and were resected after chemotherapy and radiotherapy. Histologically, they were poorly-differentiated adenocarcinoma with rosette-like tubules. The remaining one was moderately-differentiated papillary adenocarcinoma resembling bronchial surface epithelial cells without mucin (BSE type adenocarcinoma). The three adenocarcinomas which expressed chromogranin A were well- to moderately-differentiated BSE type adenocarcinomas, and stained tumor cells were distributed sparsely as neuroendocrine cells in the normal bronchial mucosa. One of them also expressed cluster 1 SCLC antigen/N-CAM. In the present study, we demonstrated the usefulness of NCC-Lu-243 in the immunohistochemical detection of adenocarcinomas with neuroendocrine features.