Expression of the Embryonal Neural Cell Adhesion Molecule N-CAM in Lung Carcinoma. Diagnostic Usefulness of Monoclonal Antibody 735 for the Distinction Between Small Cell Lung Cancer and Non-small Cell Lung Cancer

Paraffin sections of 19 surgically resected small cell lung carcinomas (SCLC), 33 non-small cell lung carcinomas (NSCLC) of various types, and four bronchial carcinoids were immunostained with monoclonal antibodies (MoAbs) 735 and anti-Leu 7, both recognizing some sugar epitopes present on the neural cell adhesion molecule N-CAM. With MoAb 735, all SCLC were stained focally or diffusely, and one carcinoid was stained focally. Only three of the 33 NSCLC were faintly and focally positive with MoAb 735; these three tumours showed relatively small tumour cells and small, oval nuclei. Anti-Leu 7 stained all the carcinoids, only eight SCLC, sometimes focally, and eight NSCLC. MoAb 735 was thus superior to anti-Leu 7 in distinguishing between SCLC and NSCLE. Since MoAb 735 stained all SCLC strongly and is applicable on paraffin sections, it provides a well-needed addition to the immunomarkers used in the diagnostic distinction of SCLC and NSCLC.