Kaposi sarcoma is a multifocal neoplasm that may involve the viscera as well as the skin. It cannot be categorized with certainty and at present must be considered a disease of unknown cause that demonstrates some features of a vascular neoplasm with a malignant potential. Kaposi lesions may undergo malignant change and metastasize. The disease is usually fatal in those patients with multiple visceral lesions.
Two patients, one with a rapid course and one with a slow course, had widespread visceral involvement as found at necropsy. There was a great variability in the histopathological appearance of the tumors, but at death most of them appeared to be angiosarcomas. The lesions on the skin were more typical histopathologically of Kaposi hemorrhagic sarcoma, although in patient 1 there was a more anaplastic type of Kaposi sarcoma in the skin.
Reed WB, Kamath HM, Weiss L. Kaposi Sarcoma, With Emphasis on the Internal Manifestations. Arch Dermatol. 1974;110(1):115-118. doi:10.1001/archderm.1974.01630070079023