A comparison has been made between two vasoformative lesions, Kaposi's sarcoma and granuloma pyogenicum, as they are encountered in Uganda. Both are predominantly skin lesions arising in the distal extremities, may resemble each other clinically, and are widespread in their distribution in Ugandan communities. They bear a reciprocal relationship to each other as regards age and sex incidence, Kaposi's sarcoma being mainly a disease of adult males and granuloma pyogenicum a disease of immature males and females. Histologically there are many similarities between them, the essential difference being the presence of a spindle-cell sarcomatous element in Kaposi's sarcoma. The clinical behaviour reflects this difference in that granuloma pyogenicum develops quickly and appears to be self-limiting, while Kaposi's sarcoma is slowly progressive and shows much less tendency to regress.On the basis of these findings it is concluded that, although these two lesions may be completely unrelated, it is possible that both represent a response of the vasoformative elements in the skin to a similar form of initiating stimulus and that hormonal or sex-linked genetic factors determine which lesion will develop in response to this stimulus.The presence of intracytoplasmic inclusion in the tumour cells of Kaposi's sarcoma might be of significance in the histogenesis of this tumour, and of value in its histological differentiation from granuloma pyogenicum.

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