Basement membrane components in mammary tumours of the dog and cat

The distribution of the basement membrane (BM) components, laminin, type IV collagen and type VII collagen were studied immunohistochemically in benign and malignant growths of the mammary epithelium of the dog and cat. Intact BMs were found in benign growths, but in well-differentiated malignant tumours they were generally discontinuous, and missing in poorly differentiated carcinomas. An increase in the histological grade of atypia was accompanied by a more marked disruption or fading of BM. Monoclonal antibody (LH 7.2) proved useful in demonstrating type VII collagen in tumours in which massive proliferation of blood vessels made the evaluation of BM features with antibodies to laminin and type IV collagen difficult. Type VII collagen is present in BM of the mammary epithelium but not under the endothelium of blood vessels; it may therefore enhance the value of BM markers as aids in the study of neoplastic progression.