Malignant solitary fibrous tumor of pleura with focal expression of cytokeratin

Solitary fibrous tumor is a rare circumscribed neoplasm involving usually t he pleura and now described in many organs and in the soft tissues with a f avorable outcome when completely excised. We report herein a malignant soli tary fibrous tumor of the pleura occurring in a 59-year-old woman. The tumo r cells strongly expressed vimentin and CD 34, in addition a weak positive staining was obtained using CD 99 and bcl 2. A disconcerting focal immunore activity with cytokeratin was observed. Solitary fibrous tumor is composed of loosely arranged spindle cells of variable density and may occasionally mimic malignant mesothelioma, an hemangiopericytoma or synovial sarcoma. im munohistochemical study is helpful demonstrating a strong positivity for vi mentin and CD 34 and absence of staining for epitheliul markers and S-100 p rotein.