[Solitary fibrous tumor of the epicardium]

A giant Solitary Fibrous Tumor (SFT) arising in the pericardium is described. A 53 year old woman was suspected to have a lung tumor and thoracotomy was performed. Intraoperatively the child-head sized mass was found to be localized in the pericardial sac. The histopathological interpretation of a small wedge-biopsy was 'endothelioma of uncertain malignancy' and heart-transplantation was performed two months later. The patient died of postoperative infection. Post mortem examination could exclude tumor rest or metastasis. The explanted heart revealed a large bulk of 2800 grams arising from the epicardium of the left chamber and enveloping the heart without invading the underlying myocardium. The histopathological pattern varied between cell-rich and -poor fibromatous areas and well capillarized endothelioma-like zones. Immunohistochemistry revealed positive reactions with monoclonal antibodies against Vimentin and CD 34 and no reactions against Cytokeratins and Faktor VIII. This pattern was confirmed in 7 SFT's of the pleura from our archives. A second control group of 7 mesotheliomas was positive for cytokeratins and vimentin but not for CD 34 and Faktor VIII. Diagnosis of SFT might be difficult because of its variability in histopathology, sometimes mimicking a hemangiopericytoma or endothelioma. Recent reports of tumor localizations devoiding serosal surfaces illustrate the diagnostic and histogenetic dilemma of this tumor. The differentiation of SFT from mesothelioma and endothelioma can be achieved by immunophenotyping including CD 34.