Stromal accumulation of chondroitin sulphate in mammary tumours of dogs

To contribute to the investigation of the composition of the extracellular matrix in epithelial tumours, mammary gland tissues of dogs (including tumo urs, hyperplasias and normal tissue as well as metastatic lesions in lymph nodes and lung) were studied histochemically and immunohistochemically for distribution of sulphated glycosaminoglycans (s-GAGs). The formaline-fixed tissue was stained by alcian blue at pH 5.8, using the 'critical electrolyt e concentration' to study the degree of sulphation of s-GAGs. s-GAGs were c haracterized by degradation with enzymes and nitrous acid and by immunohist ochemistry with two anti-chondroitin sulphate monoclonal antibodies. The li ght microscopic investigation of s-GAG deposits revealed a limited number o f patterns of their distribution. The main s-GAGs found in the mammary glan d tumours of dogs and in metastatic lesions were chondroitin sulphate (CS) and heparin/heparan sulphate (HEP/HS), CS accumulated in diffuse structures between epithelial cells as well as around clusters of tumour cells. The l atter pattern, possibly representing a mesenchymal reaction to the tumour, was present in 74% of the tumours, and in 67% of these, highly sulphated CS was present. A diffuse accumulation of CS was present almost exclusively i n complex and mixed tumours; because of the expression of the 3B3 epitope f or CS in immature cartilage the spindle cells of complex tumours are argued to be the precursors of the cartilage in mixed tumours. HEP/HS was stored mainly in mast cells that were found in increased numbers in hyperplasias a nd tumours. By pretreatment of microscopic slides with chondroitinase AC or ABC immunostaining of fibronectin could be made possible in areas in which CS was abundantly present, suggesting that CS may mask fibronectin epitope s. it is concluded that CS with different degrees of sulphation is the most important s-GAG in the extracellular matrix of mammary tumours of dogs. CS and other s-GAGs accumulate at different sites and may have a different pa thogenetic significance.