A peculiar vascular tumor of the pericardial cavity affecting a 21-year-old man is reported. The tumor was formed by spindle cells and narrow vascular channels. It was difficult to decide between primary pericardial Kaposi's sarcoma or angiosarcoma. The patient was HIV negative and no other tumors were revealed in the course of the disease. Immunohistochemical investigations showed positive endothelial markers-FVIII, CD 31, CD 34 in the tumor cells. Due to an inconclusive diagnosis of the tumor six cases of Kaposi's sarcoma and six cases of angiosarcomas were retrieved from our files, the same spectrum of immunohistochemistry as in above case applied, and the results compared. We found no significant differences in the positivity of endothelial markers among these cases and when compared with the case of pericardial tumor. The reactivity of CD 34 was, however, strong in cases of Kaposi's sarcoma whereas in angiosarcomas it yielded a weak and focal reaction only. In spite of the latter finding we feel that in individual cases, like the described tumor of the pericardial cavity, the immunohistochemical investigation cannot discriminate angiosarcoma from Kaposi's sarcoma. The reported tumor of the pericardial cavity was considered an unusual form of a low grade angiosarcoma with immunophenotypic features of Kaposi's sarcoma.

Hlavův 1 patologickoanatomický ústav 1 LF UK a VFN Praha