Kaposi sarcoma is a type of cancer that forms in the lining of blood vessels and lymphatic vessels. It often appears as purple, red, or brown spots on the skin or mucous membranes. This cancer is associated with Human Immunodeficiency Virus (HIV) infection and is more common in individuals with weakened immune systems. There are different forms of Kaposi sarcoma, including classic Kaposi sarcoma, which typically affects older men of Mediterranean descent, and epidemic Kaposi sarcoma, which is linked to HIV/AIDS. Treatment options may include chemotherapy, radiation therapy, and antiretroviral therapy to strengthen the immune system.