The changing incidence of lymphoproliferative disorders in Yorkshire

Secular trends in the incidence of lymphoproliferative disorders on North and West Yorkshire and Humberside from 1985 to 94 were studied and changes in incidence by tumour subtype were analysed. Population-based data on the incidence of lymphoproliferative disorders were obtained from a specialist registry with a high level of ascertainment. Cases of chronic lymphocytic leukaemia and plasma cell myeloma were excluded and the remaining cases classified as Hodgkin's disease and non-Hodgkin's lymphoma (NHL). NHL were subdivided by site of origin and immunophenotype. Nodal B-cell lymphomas were further classified as diffuse large B-cell lymphoma, follicle centre lymphoma, mantle cell lymphoma and miscellaneous. During the study period there was a significant increase in total lymphoproliferative disorders with an average change of 2.5% per annum equivalent to 0.84/10,0000. Most of this increase was due to an increasing incidence of extranodal B-cell lymphomas and peripheral T-cell lymphomas. A numerically small but significant increase in diffuse large B-cell lymphomas was seen. There was no significant increase in other subtypes. The increased incidence of lymphomas in the area studied is mainly due to changes in two specific subgroups. There are several reasons why changes in extranodal B-cell lymphoma and peripheral T-cell lymphoma may have been particularly affected by changing diagnostic practices. Epidemiological studies of particular subtypes of lymphoproliferative disorder facilitate the identification of environmental factors involved in the pathogenesis of these tumours.