We report a case of Kaposi's sarcoma in a young woman who presented with unusual clinical and histologic features. The unusual clinical features were the absence of cutaneous lesions; the presence of a splenic mass; and extensive involvement of the peritoneum, resulting in massive ascites and intestinal and ureteral obstruction. We postulate that the spleen was the primary site of the tumor. The unusual histologic features were the presence of both sclerotic and cavernous hemangioma variants in the same tumor and extensive areas of calcium deposits in the tumor. Such atypical clinical and histologic features can pose diagnostic difficulties for both clinicians and pathologists.