Immunohistochemical demonstration of MAM-3 and MAM-6 antigens in normal human skin appendages and their tumors.

The expression of MAM-3 and MAM-6 antigens was immunohistochemically investigated on 110 tumors of human skin appendages. Forty-two samples from tumor-adjacent normal skin appendages were also studied. MAM-3 antigens, as detectable by monoclonal antibodies (MoAbs) 67D11, 115G3, and 115H10 were present in the inner layer cells but not in the outer layer cells of normal eccrine excretory ducts. Sporadic positivity was also found in cytoplasm of apocrine acini with 115G3, while 67D11 and 115H10 were negative. MAM-6 antigens, as detectable by the MoAbs 115D8, 115F5, 139H2, 140C1, and 126E7 were found in the secretory canaliculi of normal eccrine acini and within the apical lumina at the terminal portion of ducts. Apocrine acinar cells mainly exhibited an apical staining, but a focal supranuclear dot-like staining could also be observed. A foamy reaction pattern for MAM-6 was noted in mature sebocytes. However, none of the antigenic epitopes was expressed in normal squamous epithelium or hair follicles. In benign tumors, the staining patterns for both antigens, in general, resembled their distribution in the corresponding normal tissues. However, carcinomas originating from sweat glands, sebaceous glands, and the pilar apparatus expressed both antigens in a more irregular and heterogeneous pattern. This might preferably be explained by the loss of those mechanisms controlling the antigen expression in mature, functional tissues. Conclusions from these immunohistochemical studies with regard to the histogenesis mainly of the malignant skin appendage tumors should be drawn with caution.