Malignant lymphoma of follicle centre cells with marked nuclear lobation.

Four cases of malignant B-cell lymphoma characterized by a conspicuous component of tumour cells with markedly lobatated nuclei are described. Two exhibited a follicular and two a diffuse growth pattern. The tumour cell population formed a continuous spectrum comprising both cells resembling normal follicle centre cells and multilobated lymphoma cells. Cytomorphological analysis of the multilobated cell group indicated a differentiation series from centroblast-like cells with moderately lobated nuclei to large and medium-sized cells with marked nuclear lobation which revealed features of centrocytes. In three cases (1, 3, and 4) the majority of these multilobated cells showed plasmacytoid differentiation in their cytoplasm in conjunction with the synthesis of monotypical cytoplasmic immunoglobulin. No plasmacytoid features were present in a fourth case (2). In only one case (4) monotypical surface immunoglobulin was detectable on the tumour cells. A close relationship between the multilobated tumour cells and follicle centre cells was further substantiated by the finding of a similar cell variant in the follicle centres of a control group of non-neoplastic lymph nodes. It included cells with plasmacytoid differentiation which synthesized polytypical immunoglobulin. We consider this type of B-cell lymphoma with a conspicuous component of cells with lobated nuclei as a variant of malignant lymphoma, centroblastic/centrocytic.