Pomalidomide for Kaposi Sarcoma in People With or Without HIV

Background: \- Pomalidomide is a drug that can treat cancer through several mechanisms. It is taken by mouth (orally). Pomalidomide can help treat cancer by blocking certain factors that promote tumor growth or by stimulating the immune system to attack tumor cells. It also prevents the growth of new blood vessels that help cancer grow. Researchers want to see if pomalidomide can treat Kaposi sarcoma, a rare and potentially fatal skin cancer. Because Kaposi sarcoma may be associated with human immunodeficiency virus (HIV) infection, researchers want to test the drug in people with and without HIV infection. Objectives: \- To see if pomalidomide is a safe and effective treatment for Kaposi sarcoma in people with or without HIV. Eligibility: * Individuals at least 18 years of age who have Kaposi sarcoma. * Participants may or may not have HIV infection. Design: * Potential participants will be screened with a medical history and physical exam. Blood and saliva samples will be taken and a chest X-ray will be performed. A skin biopsy of a Kaposi sarcoma lesion may be performed if one has not already been done. Other imaging studies may be performed if needed. * Participants will take pomalidomide capsules every day for 3 weeks, followed by a 1-week break. These 28 days are one cycle of treatment. * Participants will have up six cycles of treatment, unless the lesions completely resolve sooner. If there are signs of improvement after six cycles but the lesions are not completely gone, up to another six cycles of treatment may be given. * Treatment will be monitored with frequent blood tests and other studies including photograph and other imaging of skin lesions. * Participants will have regular follow-up visits for 5 years after stopping treatment....