Skin cancer. Light micrograph of a section through a Kaposi's sarcoma, a type of skin cancer that is rare in the general population but relatively common amongst AIDS patients. The tumour contains a mixture of vascular and fibrous elements. The tumours appear on the skin and can spread to other sites on the body. Radiotherapy and anticancer drugs can help to contain the cancer. AIDS (acquired immune deficiency syndrome) is a disease caused by the human immunodeficiency virus (HIV). It weakens the immune system, making otherwise trivial diseases far more serious.