Composite hemangioendothelioma arising from the kidney: case report with review of the literature.

Reported herein is a medical curiosities vascular tumor primary arising from the kidney and exhibiting unique histopathological features. A 32-year-old woman underwent a total nephrectomy of right kidney because of a mass localized in the inferior pole. Distinct from other vascular lesions, on histology the tumor had a peculiar composite pattern, consisting of benign and malignant vascular components, which were haphazardly intermixed without any definite margins. The malignant component was composed of epithelioid hemangioendothelioma (45%) and angiosarcoma (50%) with moderate differentiation. Immunohistochemically, the oval to cuboidal to spindle tumor cells expressed only endothelial markers (CD31, CD34 and factor VIII-related antigen). And the angiosarcomatous component was characterized by the presence of a greater proliferation index Ki-67. Unlike other epithelial tumors, smooth muscle actin (SMA), cytokeratin, EMA and S-100 were all negative in the epithelioid tumor cells. These findings led to the diagnosis of a low-grade vascular neoplasm with morphological features consistent with so-called composite hemangioendothelioma (CHE). At 11 month follow up the patient was alive, without evidence of tumor recurrence. CHE is an extremely rare vascular neoplasm, with borderline malignant potential, which mostly occurs in distal extremity of the limbs at the cutaneous level and, only 30 cases have been previously described until now. To our knowledge, this is the first report of CHE arising from the kidney and widens the spectrum of primary vascular tumors arising in the kidney.