Intrapulmonary localized fibrous tumor. Intraparenchymal so-called localized fibrous mesothelioma.

This report describes three cases of intrapulmonary fibromas which are histologically identical to localized fibrous tumors of pleura (localized fibrous mesothelioma). Morphologically these tumors are characterized by a haphazard proliferation of cytologically bland spindle cells separated by variable amounts of wavy hyalinized collagen. Entrapped bronchiolar and alveolar epithelium is common. These spindle cells lack expression of cytoplasmic keratin, S-100 protein, desmin, and epithelial membrane antigen, but are strongly decorated for intracellular vimentin. The clinical behavior, differential diagnosis, and histogenesis of these lesions are discussed.