The cause of Kaposi's sarcoma: an avian retroviral analog.

Changes in the epidemiologic patterns of Kaposi's sarcoma prior to and during the epidemic of acquired immunodeficiency suggest that a virus transmitted similarly to the human immunodeficiency virus (HIV) may be responsible. We propose a natural avian model for Kaposi's sarcoma. Hemangiomatosis of fowls corresponds clinically and pathologically to the human disease, with characteristics including predilection for distal skin, multicentricity with organ involvement, bleeding and recurrence after excision. Pathologic stages are also similar and include initial dissection of collagen by benign endothelial cells, the formation of large blood-filled spaces, spindle cell growth, and progression to fibrosarcomalike tumors. Avian hemangiomatosis is induced by a retrovirus of the lymphoid leukosis group and has been associated with laboratory transmission of lymphomatosis. An etiopathologic parallel should be sought in man.