Characterization of type I collagen synthesis and maturation in uterine carcinosarcomas.

Abstract

Epithelial malignancies often induce an enhanced expression of interstitial collagens in the fibroblasts within the tumor tissue and the surrounding non-neoplastic stroma. In uterine carcinosarcomas (malignant mixed müllerian tumors [MMMTs]) both the stroma and the epithelium are malignant. In this investigation, both in situ hybridization and immunohistochemical staining were applied with two different antibodies that were capable of distinguishing between newly synthesized and mature, trivalently cross-linked Type I collagen to define Type I procollagen mRNA expression and the synthesis and maturation of the corresponding protein in MMMTs. In the better differentiated parts of these tumors, in which anticytokeratins stained only clearly carcinomatous cells, Type I procollagen mRNA expression was limited to stromal fibroblasts; mature Type I collagen bundles were abundant and regular. In poorly differentiated areas, in which anticytokeratins stained only a few individual cells, Type I procollagen mRNA was expressed peculiarly by three morphologically different cell types. In addition to benign mesenchymal cells, Type I procollagen mRNA was present in atypical epithelial and mesenchymal cells. In these tumors, the collagen bundles close to the malignant cells were comprised of newly synthesized Type I collagen, with only little evidence of the presence of mature, fully cross-linked collagen. These results strongly suggest that the undifferentiated cells of MMMTs are capable of producing their own stroma with irregularly arranged collagen bundles.