An immunocytochemical study of the distribution of epithelial membrane antigen in normal and disordered squamous epithelium.

Using immunocytochemical techniques, we have investigated the distribution of epithelial membrane antigen (EMA) in human squamous epithelium. The antigen is not demonstrable in normal adult tissues although it is present on the surface membrane of normal foetal epidermis before keratinization takes place. It may be expressed strongly in the adult, however, in in situ and infiltrative squamous carcinomas as well as in a variety of non-neoplastic states. Present evidence suggests that EMA may protect exposed surfaces. The lack of demonstrable antigen on malignant melanomas and basal cell carcinomas highlights the histogenetic differences between these tumours and squamous carcinomas, and suggests a possible role for EMA in the differential diagnosis of malignant skin tumours.