Morphological and immunological definition of a malignant lymphoma derived from germinal-centre cells with cleaved nuclei (centrocytes).

Thirteen lymphomas consisting of one particular cell type were selected from 135 cases of non-Hodgkin's lymphoma. The lymphoma cells were mainly characterized by irregularly shaped nuclei and faintly stained cytoplasm. The growth pattern of the tumour was diffuse. Immunological phenotyping of suspended cells showed that the tumour cells, irrespective of whether they were isolated from lymphoma tissue or from lymphoma tissue or from peripheral blood of leukaemic cases, bore a dense layer of surface immunoglobulin, lacked cytoplasmic immunoglobulin and receptors for mouse erythrocytes, and expressed both complement-receptor subtypes (i.e., receptors for C3b and C3d) in all but one case. The exceptional case was C3b receptor-positive and C3d receptor-negative. The number of IgG-Fc receptor-bearing cells was usually small. There was a consistently small proportion of non-malignant T cells in the tumour tissue. A comparison of the properties of these lymphomas with those of other types of non-Hodgkin's lymphoma and of non-malignant lymphoid cells, shows that the cells of this type of lymphoma (a) differ morphologically and/or immunologically from the cells of all other known types of non-Hodgkin's lymphoma and (b) resemble centrocytes (cleaved follicular-centre cells) of reactive germinal centres. Thus, this type of lymphoma appears to be an entity that is closely related to, or even derived from, centrocytes.