Abstract

Localized fibrous tumors are rare neoplasms that most often involve the pleura The histogenesis is still controversial: specialized submesothelial or fibroblastic origin. The incidence has not been clearly linked to asbetos exposure. We experienced a case of solitary fibrous tumor of the pleura with a very prominent small cell component in a 68-year-old male. The mass was found in the right chest incidentally on routine chest X-ray. On chest CT, a well-circumscribed homogeneous low density mass was attached to the right parietal pleura and measured 10 x 9 x 7 cm in dimension. On operation, the mass was attached to the upper parietal pleura and focally adhered to the right upper lobe. Grossly, the mass was ovoid, firm, and encapsulated by a thin translucent glistening membrane, and measured 13,5x 9x 7cm in dimension. The cut surface was mostly grayish-yellow, firm, and focally variegated with hemorrhage, necrosis, cystic change, and myxoid area. Microscopically, irregular aggregates of small round cells predominated and were admixed with cellular spindle cell areas, dense collagenous areas, and angiofibroma-like areas. It also showed focal necrosis and mitosis of 1/10HPF. On immunohistochemical staining, vimentin was positive, but cytokeratin, EMA, LCA, chromogranin, and NSE were negative. Electron microscopy showed fusiform to round tumor cells with scanty cytoplasm in close apposition to focal collagen. The nuclei were euchromatic or heterochromatic. The cytoplasm contained a small amount of organelles. Focal primitive intercellular junctions were identified.

• Keywords: Localized(solitary) fibrous tumor of the pleura, Prominent small cell component, Specialized submesothelial cell