Non-Hodgkin's lymphomas: An immunohistochemical and histological study

Abstract

Immunohistochemical and histological studies were performed on paraffin sections of 19 cases of non-Hodgkin''s lymphoma (NHL). All the cases were lymphocytic in type, 11 were follicular (6 small, 3 mixed and 2 large cell types) and 8 were diffuse (4 intermediate, 3 poorly-differentiated and 1 well-differentiated types). Dendritic histiocytes were found in and around the follicles of follicular lymphomas. The distribution of the dendritic cells within the neoplastic follicles resembled that in reactive follicles, supporting the concept of an origin for lymphoma follicles from their reactive counterparts. In the diffuse lesions the dendritic cells were large and more pleomorphic than in the follicular lesions, but these features were not so pronounced as those previously observed in Hodgkin''s disease. The PAP [peroxidase-antiperoxidase] sequence showed Ig [immunoglobulin] in the lymphoma cells. Monotypic Ig was most commonly found in follicular lymphomas, .mu..kappa. secretion being the most frequent combination of H and L chains. Most cases (73%) were thus clearly derived from B [bone marrow-derived] lymphocytes. Since monoclonality was evident in only a proportion of cases, then that lymphomas may be polyclonal initially and monoclonality is a later development. Normal mature plasma cells containing a high concentration of intracellular Ig were present in all but 1 of the lesions. The Ig was polytypic, cells containing .kappa. and .lambda. chains being present in roughly equal numbers and .gamma. chains predominating. Extracellular Ig (.gamma., .mu., .kappa., .lambda.) was present in many lesions. Small nonlymphomatous lymphocytes were present in all cases. In 8 lesions these had polytypic surface Ig (.mu., .kappa., .lambda.). Dendritic cells mingled with these lymphocytes. Collections of small lymphocytes nonreactive for Ig were present. These had no association with dendritic histiocytes and might have been T [thymus-derived] cells. In most cases, immunohistochemistry alone provides an insufficient basis for the diagnosis of lymphoma. Disturbance of cellular morphology and tissue architecture remain the most useful criteria for the diagnosis of lymphoma.