Malignant skin tumours as seen at K.N.H. over a 10 year period (1977-1986)

Abstract

During the period of this study (1977 - 1984) 9886 malignant tumourswere recorded in the Kenya cancer registry. Of these, carcinomaof cervix was the number one tumour. It formed 15% of all tumours.Carcinoma of the skin (including SCC and BCC) was number two forming 10.2% of ali tumours. Malignant melanoma formed 3.9%. The least frequent tumour was Carcinoma of rectum at 1.3%. In Nigeria a similar study showed that a total of 6133 malignant tumours were recorded in their Cancer Registry in a period of 8 years and the relative frequencies of the different tumours is given in Table VI. There is conflicting evidence about the incidence of skin cancer in pigmented races, including Africans. Shapiro and Colleagues in 1953 found 50 (8.4%) cases of skin cancer out of 590 cases of malignant disease in South African Bantus, over a period of 3 years. He concluded that it was a rare condition. Stainer in 1954 found only one American Negro with carcinoma of scrotum in Los Angeles out of 135 patients. Schrek in 1944 found that skin cancer accounted for only 3% of tumours in American Negroes. Davies and his colleagues in 1968 found that superficial cancers of skin constituted up to 15% of all cancers diagnosed in Uganda Africans. A survey carried out by National Cancer Institute of U.S.A. in 1947 - 48, the crude incidence rate of skin cancer in non-whites was about one-sixth to one-twentieth that of whites. Low ratio frequencies have also been obtained in other pigmented races in India (Khanolkar 1950), Indonesia (Kouwenaa and Sutomo 1957), North Africans (Mussini and Montpellier 1951).In developing countries record keeping and demographic data are either not accurate or not available. Most of the quoted studies have been done mainly in the nineteen fifties and sixties. These studies do need updating. Data obtained from these studies may have been affected by standard of primary health care, diagnostic facilities and criteria and socio-economic status of the population studied. As such comparison should not be parallel, all the same these results are increasingly useful with a view to identify factors suspected of carcinogensity in these tumours. One point that is clear in all these studies is the relatively low incidence of skin cancer in Blacks compared to caucasians. In the Caucasians the incidence is again higher in Europeans who have migrated to the tropics compared to those in temperate climates. The aetiological factors in development of skin cancers in Blacks is not alltogether clear. The only factor that has stood the test over the years is that skin pigment seems to protect the Blacks from the baneful effects of sunlight. Malignant melanoma has been shown in this study to be more aggressive in the Black population. The aetiological role of trauma in development of malignant melanoma is shown but it does appear to be a procarcinogen and not carcinogenic in its own right. It is not clear what makes skin cancers to be more aggressive with poor prognosis in the Blacks. Late presentation alone does not seem to be the only reason for this. A critical look at the immune system especially in the Blacks may probably give an answer to most of these unanswered questions.