Geographical differences in the distribution of malignant tumours. Trends in research on the etiology of human tumours.

Malignant tumours are encountered among all races and in every type of geographical zone, but there are marked differences in different areas in the prevalence of particular forms of tumour-differences that are to a greater or lesser extent dependent on factors such as the climate and geography of the region and the habits, customs and occupations of the people. The study of these factors in relation to the occurrence of malignant tumours is of great importance in reaching an understanding of the etiology of tumours in man.In this paper the author discusses the many problems involved in the study of regional features in the prevalence of malignant tumours, with special reference to the difficulties of ensuring comparability of the data from widely differing regions and population groups. He concludes the paper with a review of some known facts regarding the distribution of malignant tumours at various sites in which he compares data obtained in surveys in the USSR with those obtained in other countries.