Geopathology of endemic pediatric lymph node Kaposi's sarcoma in Western Kenya.

Abstract

We conducted an epidemiological and histological analysis of the endemic lymph node-type Kaposi's sarcoma (KS) in African children (under 16 years old) in Western Kenya in order to determine the ethno-geographical distribution of the disease and to clarify its histological features and histogenesis during the 12-year period between 1979 to 1990. The age distribution of all endemic type KS in Western Kenya showed two age peaks; one in early childhood and the other in middle to advanced age. Most endemic KS in children initially occurred in the lymph nodes, while that of people of middle to advanced age showed a primary lesion in the skin. The male to female ratio of the endemic KS was 3.1 to 1 (in all pediatric types), 3.4 to 1 (in the pediatric lymph node-type) and 10.8 to 1 (in all adult types). A high incidence of the lymph node-type KS in children was observed in the Luo group ethnically and in Nyanza Province around Lake Victoria geographically. The lymph node-type KS originated at the paracortical areas and gradually grew along the reticulin network originating from the trabeculae. The lesion of KS histologically consisted of several types of cells, especially spindle-shaped cells, macrophage-like cells and immature endothelial cell-like cells and was accompanied by almost normal small blood vessels, lymphatic vessels and postcapillary venules. No abnormal mitoses were observed in any of the cells. There were no primary necroses due to tumor proliferation and also no extracapsular invasions. Immunohistochemically, spindle-shaped cells, immature endothelial cell-like cells and mature endothelial cells were positive for Vimentin, but only mature endothelial cells were positive for Factor-VIIIRa and UEA-1. Macrophage-like cells were positive for Factor-XIIIRa. These findings suggested that : 1) there are certain differences in the etiological co-factors of KS between the endemic lymph node-type KS in children and the endemic cutaneous type KS in adults, 2) KS cells originate from pluripotent mesenchymal cells and 3) KS might not be a malignant tumor, but rather a benign neoplasm, tumor-like lesion or reactive hyperplasia.