Ethnogeographical coincidence of endemic Kaposi's sarcoma and African Burkitt's lymphoma in western Kenya.

Abstract

Geopathological studies on endemic Kaposi's sarcoma (KS) and African Burkitt's lymphoma (BL) in western Kenya were performed, and revealed that KS and BL had relatively same geographical and ethnical distribution. The western region of Kenya stands almost exactly astride the equator. It accounts for almost one third of the whole country in area and about one half in population. Western Kenya is composed of three provinces; Nyanza Province, Western Province and Rift Valley Province. Out of 25, 343 surgical pathological specimens at provincial hospitals in Nyanza, Western and Rift Valley for 8 years during 1979 to 1986, 124 and 135 cases were histologically diagnosed as KS and BL respectively. Frequency in all malignant tumors was 2.92% (KS) and 3.18% (BL). The high incidence of KS was found between the age of 50 and 59, while all BL cases were found under 22 years. The male to female ratio was 8.4 : 1.0 in KS and 1.2 : 1.0 in BL. The incidence of KS and BL per 100, 000 population in each province is as follows : a) 2.12 (KS) and 3.54 (BL) in Nyanza Province, b) 1.80 (KS) and 1.20 (BL) in Western Province, and c) 1.11 (KS) and 0.68 (BL) in Rift Valley Province. Nyanza Province and Western Province are tropical savannah areas, whereas Rift Valley Province is a tropical highland. The incidence of KS and BL per 100, 000 population among main ethnic groups in western Kenya is as follows : the Luo, the main inhabitants of Nyanza Province around Lake Victoria, showed the highest incidence of KS (2.56) and BL (4.35), followed by the Luhya, the main inhabitants of Western Province, the Kalenjin, the inhabitants of the tropical highland in Rift Valley Province, and the Kisii, the inhabitants of highland area of Nyanza Province. The Luo are descended from the Nilotic groups and the Luhya belong to the Bantu. No case of KS and only a few cases of BL were found among the inhabitants of desert or semi-desert areas. No other tumors showed above mentioned characteristics. The geographical and ethnical coincidence of KS and BL was more clear in the child population than in the adult. These results suggest that there is a geographical coincidence of KS and BL based on same etiological cofactors including high temperature, high humidity, unknown transmissible agents, and probably genetic factors and life styles. This was mainly demonstrated in Nyanza Province around Lake Victoria in western Kenya.