[Solitary fibrous tumor of the pleura; report of a case].

An 81-year-old male appealed against a feeling of dyspnea, and consulted the hospital. The giant tumor discovered in the thorax and it was enlarging gradually for 7 years. The tumor shadow with a diameter of about 15 cm was noted in right lower lung field on the chest X-ray. A definite diagnosis was not obtained by the needle biopsy. The tumor was found to exist between upper lobe and lower lobe and pressed lower lobe at surgery. The tumor was completely excised with partial resection of the collapsed lower lobe. The tumor was 1,050 g in weight and 18 cm in maximum diameter. Pathological examination showed the irregular and plan-like arrangement of the spindle-shape cell. Immunohistochemical study revealed positive findings for bcl-2 and CD34, negative findings for desmin, ketatin, and alpha-actin. The tumor was diagnosed as malignant solitary fibrous tumor of the pleura due to highly atypical nuclear finding with an abundant nuclear fission or histology.