A 22-kd surface antigen detected by monoclonal antibody E 48 is exclusively expressed in stratified squamous and transitional epithelia.

After immunization of mice with viable cells of a metastasis of a laryngeal squamous cell carcinoma, a monoclonal antibody E 48 was obtained that detects an epitope present exclusively in squamous and transitional epithelium and their neoplastic counterparts. Immunoblotting revealed that E 48 recognizes a 22 kd molecule. Seventy-five of 76 squamous cell carcinomas from the head and neck, lung, cervix, and skin stained positively, whereas various adenocarcinomas from the colon, lung, and breast, and small cell lung carcinomas consistently stained negatively. The E 48 antigen, which is formaldehyde resistant, appears to be a reliable marker for differentiation of squamous cell carcinomas from adenocarcinoma, and small cell carcinomas.