a multicentric, malignant neoplastic vascular condition characterized by blue to red nodules under the skin, usually on the lower limbs, especially the toes or feet; the nodules slowly increase in size and number and spread to more proximal sites. Tumors may remain confined to skin and subcutaneous tissue, or may become more widespread and involve the viscera. The condition occurs endemically in certain parts of Central Africa and Central and Eastern Europe, and a virulent, disseminated form occurs in immunocompromised patients. Human herpesvirus 8 has been implicated as a causative agent.