Basement membranes in experimentally induced skin tumors.

Basement membrane changes in the epidermis and hair follicle apparatus resulting from topical 9,10-dimethylbenzanthracene applications were studied in mice, rats, and hamsters by light and electron microscopy and using antibodies to human collagen type IV and laminin. The basement membrane was distinct in epidermal hyperplasia, dysplasia, and papillomas, as well as around most of the keratoacanthomas and squamous cell carcinomas, which showed basement membrane irregularities, thickening, and reduplication in some areas. The invading edges of the squamous cell carcinomas with inflammatory infiltrates were devoid of laminin and collagen. Collagen IV and laminin-positive structures were observed around preserved follicular structures in rat: hair nevi and hair-follicle nevi, but partly absent around trichoepitheliomas and trichofolliculomas. Basal cell tumors were usually surrounded by a distinct basement membrane, which was lacking around some tumor cells.