The changing incidence of lymphoproliferative disorders in Yorkshire

Secular trends in the incidence of lymphoproliferative disorders on North a nd West Yorkshire and Humberside from 1985 to 94 were studied and changes i n incidence by tumour subtype were analysed, Population-based data on the i ncidence of lymphoproliferative disorders were obtained from a specialist r egistry with a high level of ascertainment. Cases of chronic lymphocytic le ukaemia and plasma cell myeloma were excluded and the remaining cases class ified as Hodgkin's disease and non-Hodgkin's lymphoma (NHL). NHL were subdi vided by site of origin and immunophenotype. Nodal B-cell lymphomas were fu rther 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 aver age change of 2.5% per annum equivalent to 0.84/10 0000. Most of this incre ase was due to an increasing incidence of extranodal B-cell lymphomas and p eripheral 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 studie d is mainly due to changes in two specific subgroups, There are several rea sons why changes in extranodal B-cell lymphoma and peripheral T-cell lympho ma map have been particularly affected by changing diagnostic practices. Ep idemiological studies of particular subtypes of lymphoproliferative disorde r facilitate the identification of environmental factors involved in the pa thogenesis of these tumours.