Kaposi's sarcoma: evidence supporting its origin from the lymphatic system.

The histogenesis of Kaposi's sarcoma (KS) remains a subject of dispute. The weight of evidence, however, favors derivation of the spindle cell of KS from the lymphatic system and very likely from lymphatic endothelium. This conclusion is based on light microscopic and morbid anatomical observations and is further supported by the unique distribution of lesions in the skin, and in the submucosa of the gastrointestinal tract, following the lines of lymphatics; by the remarkable predilection of KS for lymph nodes (often without skin lesions); by the absence of lesions in organs which are devoid of lymphatics, i.e. the brain and eyeball; and by observations made by the author and others, utilizing electron microscopy, enzyme histochemistry and immunohistochemistry. It is recognized nonetheless that reactive elements such as fibroblasts, myofibroblasts and histiocytes may also be involved in the proliferative process.