A malignant neoplasm characterized by a vascular proliferation which usually contains blunt endothelial cells. Erythrocyte extravasation and hemosiderin deposition are frequently present. The most frequent site of involvement is the skin; however it may also occur internally. It generally develops in people with compromised immune systems including those with acquired immune deficiency syndrome (AIDS). The disease is MONDO_0005055 (Kaposi's sarcoma). Also known as: KS, Kaposi sarcoma, Kaposi's sarcoma (disease), Kaposi's sarcoma of conjunctiva, Kaposi's sarcoma of cornea, Kaposi's sarcoma of lung, Kaposi's sarcoma of palate, Kaposi's sarcoma of soft tissue.