evidence: Kaposi sarcoma (Kaposi’s sarcoma) is cancer that starts in cells that line lymph and blood vessels. It causes lesions on people’s skin or tissue that lines their internal organs. It typically affects people with weakened immune systems who also carry human herpesvirus 8 (HHV-8). Healthcare providers can treat this condition, but it may come back. Kaposi sarcoma (Kaposi’s sarcoma) is a form of soft tissue sarcoma. It affects people with weakened immune systems who also carry the rare virus human herpesvirus 8 (HHV-8). The virus turns healthy cells into cancerous cells. There are different types of Kaposi sarcoma, but all types cause cancerous lesions (tumors) on people’s skin. Healthcare providers can treat this condition, but it may come back. [...] Kaposi sarcoma in the United States is rare. People develop Kaposi sarcoma because they carry HHV-8 and have weakened immune systems. Kaposi sarcoma affects 6 in 1 million people with HIV/AIDs and 1 in 200 people taking immunosuppressants after stem cell (bone marrow) transplant or organ transplant surgery.