ABSTRACT
Non-Hodgkin’s lymphoma (NHL) encompasses a heterogeneous group of tumours of the lymphoid system. The worldwide incidence is approximately 10 cases per 100 000 person years, although this is increased in Western countries with the highest figures reported in the United States (Fig. 43.1). Data from the USA and Europe have indicated that the overall incidence of NHL rose by 3-4 per cent per year between the 1970s and 1990s although the rate of rise appears to have slowed during the last decade.1,2 Despite the identification of many risk factors for the development of NHL, the reason for this changing pattern is unclear. Lymphomas of all types are more common in the elderly (Fig. 43.2) making this an increasing health-care problem in an ageing population, and they have an uneven sex and racial distribution, occurring more frequently in men and people with a black African ancestry.2
