Localized fibrous tumors of pleura: A light and electron microscopic study

Abstract

Light and electron microscopic studies of two localized fibrous tumors of pleura are presented. The tumors showed microscopically a purely fibrous character without preformed slit‐like spaces, or papillary or tubular structures. The neoplasms were encapsulated, pedunculated, and projected freely into the pleural cavity. Fine structural studies showed fibroblasts with prominent rough endoplasmic reticulum, intracytoplasmic bundles of fibrils, and elongated cytoplasmic processes. Desmosomes, microvilli, or basement membrane‐like material was not observed. Although fibrous tumors of pleura are generally regarded as mesotheliomas, there are those in which the cell components are purely fibroblastic in nature, without light microscopic or ultrastructural resemblance to mesothelial cells. They derive probably from fibroblasts normally present underneath the visceral pleura, as suggested by the presence of a fibrous capsule covered by an intact mesothelial cell lining. It is proposed to name those neoplasms “localized fibrous tumors of pleura,” without implying their mesothelial origin unless mesothelial cells are demonstrated within the tumor tissue. Encapsulated fibrous tumor of pleura are usually benign and adequately treated by local excision. Copyright © 1974 American Cancer Society