Histological transformation of non-Hodgkin's lymphoma: a prospective study.

Forty-three lymph node biopsies were performed prior to retreatment in 30 unselected patients who had relapsed following chemotherapy for advanced non-Hodgkin's lymphoma of low grade histological type. Eight patients (27%) showed unequivocal evidence of transformation to a high grade variety of lymphoma. These included 4 out of 21 cases originally having had follicular lymphoma and 4 out of 9 cases having had diffuse lymphoma. In 2 further patients with follicular lymphoma, relapse was diagnosed following examination of the bone marrow and in one the tumor had clearly transformed. In 5 of the transformed lymphomas the cell type was predominantly centroblastic, in 2 immunoblastic and in the remaining 2 centrocytic (anaplastic). Five of the 9 cases developing high grade lymphoma have died after a median interval of 5 months from transformation, whereas only 3 of 23 cases showing no change are dead. In 4 patients low grade lymphoma persisted in the bone marrow at the time of nodal transformation. The clinical circumstances at the time of rebiopsy were unhelpful in predicting transformation.