Malignant melanoma in Nigeria-pathological studies

Pathological features of twenty-one cases of malignant melanoma studied in the University of Nigeria Teaching Hospital, Enugu during the period January, 1974 to December, 1975 are presented. Malignant melanoma accounted for 2.4% of all tumours and 4.5% of all malignant tumours, greatest age incidence being in the fifth to seventh decades. The male to female sex ratio was 2:1. 73.2% of cases were of the nodular variety. 81% melanomas occurred on the sole of feet validating the hypothesis that the pigmented skin in Africans is resistant to malignant melanoma. Melanoma in Nigerians would appear essentially to be arising from epidermal melanocytes and not from preexisting naevus cells. Hence we do not feel prophylactic removal of plantar moles as suggested by Onuigbo (1975) is desirable. Histologically, there was no clear association between the cell types and the kind of melanoma or invasion of the tumour. The difference in behaviour and natural history of malignant melanoma would appear to have a bearing on the local tissue and also general immune mechanisms of the host.