BackgroundClassic Kaposi’s sarcoma is a lymphatic endothelial cell neoplasm usually present on the skin of the upper and lower extremities. Although it commonly affects human immunodeficiency virus positive patients, there have been some human immunodeficiency virus negative cases reported. We report an uncommon presentation of stage IV classic Kaposi’s sarcoma in an human immunodeficiency virus negative patient in Latin America with complete clinical response using only radiation therapy treatment.Case presentationA 78-year-old Mexican man with no evidence of human immunodeficiency virus infection presented with a painful widespread dermatosis with maculopapular, nodular, violaceous lesions on his legs and ulcerated lesions on his feet. A biopsy confirmed the lesions as classic Kaposi’s sarcoma. Radiotherapy treatment was delivered, prescribing a total dose of 30 Gy in 15 fractions with a complete clinical response within 15 months of follow-up.ConclusionsThis is an unusual case since it is uncommon to use radiation therapy as the single treatment in stage IV classic Kaposi’s sarcoma; the efficacy of the treatment is shown in the impact in our patient’s recurrence-free survival, local control, and palliation of our patient’s symptoms.