Immunohistochemical localization of extracellular matrix components in human breast tumours with special reference to PG-M/versican.

Immunohistochemical localization of the large proteoglycan, PG-M/versican, was studied in 36 breast tumours, including infiltrating ductal carcinomas, benign tumours and fibrocystic diseases. The relation between the proteoglycan and the other extracellular matrix components was also investigated. In the carcinoma tissues, the interstitial elements of the 'specific stroma', consisting of fibroblastic cells and fine fibrils, were reactive to antibody 2B1, which specifically recognizes the large proteoglycan, PG-M/versican. In the peripheral invasive areas of infiltrating ductal carcinoma, the most intense 2B1-positive reaction was visualized in mesenchymal tissues between carcinoma cells clumps and the surrounding tissues, where hyaluronic acid could be demonstrated histochemically. The 2B1-positive elements were not reactive to antibody 6B6, which specifically recognizes small proteoglycan. In the central sclerotic areas, where antibody 6B6 was reactive, a 2B1-positive reaction was detected only in elastosis masses, which also bound antibodies to type IV collagen and laminin, and to some extent antibody raised against chondroitin 6-sulphate proteoglycan. Elastic tissues of blood vessel walls and perivascular elements became reactive to antibody 2B1 when they were involved in carcinoma invasion. The present results have shown that PG-M/versican was localized in the proliferating interstitial tissues, in particular in hyaluronic acid-rich portions, in association with carcinoma cell growth, and also that PG-M/versican accumulated in vascular and perivascular elastic tissues involved in carcinoma invasion. The biological significance of PG-M/versican was briefly discussed.