Human B Cells: Differentiation and Neoplasia

An original perifollicular zone cell in the canine reactive lymph node: a morphological, phenotypical and aetiological study

In this study of 109 canine reactive lymph nodes, the perifollicular zone (PZ) cell was characterized by cytological, histological, immunocytochemical and electron microscopical techniques. The PZ cell was always found in association with plasma cell hyperplasia. Its main cytological characteristics were medium size, fine chromatin and a large central prominent nucleolus with a small amount of pale cytoplasm. It was located in a clearly recognizable PZ surrounding the follicles; this zone was particularly well developed at the capsular pole of the lymph node. Electron microscopical findings indicated a poorly differentiated cell. Immunolabelling indicated a CD3-, cIg-, Ki-67- immunophenotype, suggesting a resting B cell. These results suggest that the PZ cell belongs either to a post-follicular stage between large immunoblasts and plasma cells or, as is more likely, to a pre-follicular lymphoid subpopulation occurring early in the B-cell differentiation scheme, as with most human marginal zone (MZ) cells. Its high frequency of occurrence in reactive lymph nodes in mammary tumour lymphadenopathies, systemic lupus erythematosus and leishmaniasis, suggests that the PZ cell has a special role in the canine immune response, or perhaps in the arrested maturation of the normal developmental process.

Splenic lymphoma with villous lymphocytes: natural history and response to therapy in 50 cases

We studied the natural history and response to treatment in 50 patients with splenic lymphoma with villous lymphocytes followed for a minimum of 6 months and up to 15 years (median 3.7 years). The disease occurs in the elderly (median 68 years) and affects males more than females (M/F ratio 1.77). The median survival for the group was not reached but 82% were surviving at 3 years and 78% at 5 years. Twelve patients (24%) died, one-third of deaths were disease related (four patients) and one-half were due to cardiovascular disease or another malignancy (six patients). The outcome was worse for males (31% died) than females (11% died). Fourteen patients were not treated and 10 remain alive between 1 and 6 years from diagnosis. The remaining patients were treated by chemotherapy, splenic irradiation or splenectomy. The response to chemotherapy was poor and only eight of 22 (36%) patients treated achieved a good response. Splenic irradiation was employed in seven patients and three benefited from it. Splenectomy seems to be the treatment of choice, with significant improvement seen in 19 of 20 patients with one post-operative death. This response, lasting from 6 months to 7 years (median 4 years), was seen irrespective of whether splenectomy was the initial treatment or used later in management.