[Localized fibrous mesothelioma of the pleura. Morphological studies of 7 cases]

Abstract

Localized tumors of pleura should clearly be separated from diffuse pleural mesotheliomas due to clinical and pathological peculiarities. But there is some dispute on their proper interpretation and hence disagreement about their correct designation. Some call them "fibrous tumors (fibromas)" of pleura and appreciate by this term the fibroplastic potency of tumor cells and the lacking relation to overlying mesothelial surface cells, others prefer the name "fibrous mesothelioma" and allude to an at least abortive mesothelial differentiation within the tumor tissue. Examining 7 own tumor cases by means of light microscopic, topo- and immunohistochemical as well as electron microscopic methods the investigations were aimed at analysing the morphological structure of these tumors and subjecting it to a critical reappraisal with regard to a suited designation. Histologically, a marked variability of histological structure and texture was found, there were regions with similarities to fibromas, fibrous histiocytomas, hemangiopericytomas and nerve sheath tumors as well as blastema-like areas. Occasionally a vasoformative activity could be seen. In three tumors a few epithelioid cell complexes were visible, but neither keratin intermediate filaments nor UEA-I reactivity was to be demonstrated by immunohistochemistry. Antibodies against factor VIII associated antigen only marked endothelial cells of vascular structures. By the electron microscopic examination of 1 case abortive mesothelial differentiations were visualized (some lumen-like space formations, stub-like cellular projections of the cavity facing side, primitive intercellular junctions and fragmented basal lamina-like material). The findings inclusive the immunohistochemical results are discussed and jointly taken for sustaining the interpretation of these tumors as mesotheliomas and for militating against the classification as simple pleural fibromas or fibrous pleural tumors, respectively.