[Polypoid pseudosarcomatous carcinoma. Histogenesis with evidence of myofibroblastic response (author's tranls)]

Three polypoid pseudosarcomatous carcinomas (PPSC) of the oesophagus, larynx, and urinary bladder were studied by electron microscopy to determine their histogenesis and the cellular associations which might contribute to their relative clinical benignity. In addition to a polypoid, exophytic growth, the three shared similar light microscopy features : surface ulceration, a minimal invasive epithelial component and prominent spindle-cell proliferation in association with reticulin and collagen. Three cell types were identified ultrastructurally : 1. - spindle and polygonal cells demonstrating tonofilaments and plasma membrane specialization, denoting an epithelial origin; 2. - cells identical to the first type, but with cytoplasm containing intracellular collagen ; and 3. - myofibroblasts characterized by a rough endoplasmic reticulum, prominent Golgi complexes and well formed bundles of myofilaments. The latter constituted the principal cellular component of the tumors. These findings demonstrate that the stroma of the PPSC is dominated by myofibroblasts, which probably synthesized much of the collagen associated with these neoplasms. It is suggested that the myofibroblasts signify an expression of host reactivity to the invasive carcinoma and constitute a beneficial response which contains and restricts local and vascular invasion by neoplastic cells, this contributing to the relative benignity of the neoplasms.