Kaposi's sarcoma (KS) is a type of cancer that can form masses in the skin, lymph nodes, or other organs. The skin lesions are usually purple in color. They can occur singularly, in a limited area, or be widespread. It may worsen either gradually or quickly. Lesions may be flat or raised. Human herpesvirus 8 (HHV8) is found in the lesions of all those who are affected. Risk factors include poor immune function, either as a result of disease or specific medications, and chronic lymphedema.