Increasing incidence and descriptive epidemiology of extranodal non-Hodgkin lymphoma in parts of England and Wales.

INTRODUCTION The incidence of non-Hodgkin lymphoma (NHL) arising from extranodal tissue has been reported to be increasing in Western countries and yet the epidemiology of this heterogeneous disease has been poorly described. PATIENTS AND METHODS : Cases of extranodal NHL were reported to a specialist population-based registry covering neoplastic hematological conditions in parts of England and Wales from 1986 to 1993. RESULTS Nearly one third of all NHL, 3556 cases, were extranodal in origin giving a world standardised incidence rate of 1.9/10(5) per year. The most common sites were the skin, stomach and small intestine and high-grade malignancies were predominant. An excess in male incidence was observed for extranodal NHL overall, at all ages, and for most sites. Time-trend analyses indicated significant increases in incidence for all extranodal NHL and NHL of the gastrointestinal tract, skin, central nervous system and male genital organs. Incidence rates increased proportionally more for middle-aged persons, especially females, and for skin lymphomas excluding mycosis fungoides and Sezary disease. CONCLUSION These results suggest that the rise in incidence of extranodal NHL may be due, at least in part, to an increase specifically in B-cell skin lymphomas and that particular environmental factors such as sunlight might be involved rather than the increases being the results of improvements in diagnostic practices.