Immunohistochemical studies on epithelial cells in mixed tumor of the skin

We performed studies on the lectin-binding pattern in epithelial tumor cell components of 4 cases of mixed tumor of the skin developing on the face in addition to identification of keratin and carcinoembryonic antigen (CEA), compared with those of normal sweat glands. Normal eccrine glands showed specific labelling with Dolichos biflorus agglutinin (DBA) and soybean agglutinin (SBA), whereas none of the studied lectins reacted specifically with normal apocrine glands. In mixed tumors the dark cells, which form the inner layer of the tubuloalveolar and ductal structure, showed the presence of keratin and CEA, as well as of specific sugar structures that bind to DBA and SBA. On the other hand the light cells that form the outer layer of the tubular structures or the solid epithelial cell nests gave only a faint to moderate staining of keratin, and no staining of CEA or lectins. It is probable that the inner dark cells differentiate toward the cells that have the same sugar structures on the cell surface as those of the normal eccrine gland cells, while the outer light cells appear to be immature or in a less differentiated state.