THE EXTRACELLULAR-MATRIX IN SARCOMATOID CARCINOMAS OF THE BREAST

The distribution of the main extracellular matrix components has been investigated immunohistochemically in four cases of breast sarcomatoid carcinomas. The histogenesis of these tumours is still unclear, but m ost evidence suggests that the sarcomatous component originates from m esenchymal conversion of carcinomatous cells. We found that carcinomat ous portions of the tumours were associated with linear basement membr ane-like deposition of laminin, type IV collagen and heparan sulphate proteoglycan that partially circumscribed the epithelial nests. The sa rcomatous components produced an extracellular matrix immunoreactive t o fibronectin, type I, III and VI collagens and tenascin. However, in two cases, in some sarcomatous areas, focal pericellular staining for antibodies to laminin and type IV collagen was seen. These results ind icate that modifications observed in the double tissue component of th ese tumours involve not only the cell shape and the cytoskeleton, but also the components of the extracellular matrix. The significance of t hese findings and their relevance in the understanding of the phenotyp ic pattern changes of these biphasic tumours are discussed.