[Localized fibrous tumor of the pleura. 2 case reports and differential diagnoses].

The localized fibrous tumors of the pleura are rare neoplasms, also known as "benign pleural fibromas" or "localized mesotheliomas", but those names are inaccurate. The tumors are composed of undifferentiated mesenchymal cells, intermediate and differentiated fibroblasts and collagenous interstitial tissue. Their origin is normally the submesothelial layer of the visceral pleura. Mesothelial differentiation is not present. The grading of malignancy doesn't correlate with final outcome, adequacy of surgical excision being the most important factor. This neoplasm may recur but retain its basical histologic features. The positive results for vimentin and negative results for cytokeratin antibodies help to distinguish the localized fibrous tumors from the mesothelioma. We present too cases and their diagnostic possibilities.