CARDIAC PAPILLARY FIBROELASTOMA - AN IMMUNOHISTOCHEMICAL INVESTIGATION AND UNUSUAL CLINICAL MANIFESTATIONS

Cardiac papillary fibroelastoma (CPF) is a morphologically distinctive , but rare, cardiac lesion that is usually found incidentally at autop sy or during open heart surgery. Because of improved diagnostic imagin g techniques, the premortem or preoperative diagnosis of CPF is becomi ng more frequent. The histogenesis of CPF, however, remains controvers ial. Herein we report an immunohistochemical investigation of 11 cases of CPF; two cases showed unusual embolization phenomena, including on e with histologically documented pulmonary arterial embolism. For comp arison, nine cardiac myxomas (CMs) and eight examples of organizing th rombi were also studied. Immunohistochemical markers included keratin, vimentin, collagen type TV, muscle-specific actin, desmin, factor VII I-related antigen, CD34, and S-100 protein. The cells covering the sur face of both CPFs and CMs were positive for vimentin, factor VIII-rela ted antigen, and CD34, in keeping with their presumed vascular endothe lial origin. Interestingly, the surface lining cells were also positiv e for S-100 protein in all CPF and in eight of nine CMs. In CPF, colla gen type TV showed multilayered linear staining beneath the surface th at was virtually identical to the staining pattern for elastic tissue. The major immunophenotypic difference between CPF and CM is the frequ ent presence of muscle-specific actin in the stellate cells of the str oma in CM but not in CPF. Although this study did not clarify whether CPF is a hamartomatous, neoplastic, or reparative process, it demonstr ated active participation of the surface endothelial lining cells with excessive formation of basal membrane material in the formation of CP F.