Malignant lymphoma with a high content of epithelioid histiocytes (so-called Lennert's lymphoma). Immunocytochemical and ultrastructural observations.

The clinicopathological findings of four cases of an uncommon form of non-Hodgkin's lymphoma called malignant lymphoma with a high content of epithelioid histiocytes (MLHH) are described. In each case the peroxidase antiperoxidase technique was used for detecting cytoplasmic immunoglobulins (CIg) in the diagnostic lymphoid tissue. In one case (patient 1), IgG and IgM heavy chains and kappa light chain were detected in 30 to 40 percent of the atypical lymphoid cells. This result suggests that the proliferating B lymphocytes in this patient with MLHH are neoplastic rather than reactive in nature. We were unable to identify CIg in the proliferating lymphoid cells of the other three patients. Our case when coupled with others reported in the literature suggest that the morphologic features of MLHH (so-called Lennert's lymphoma) can be associated with a neoplastic proliferation of either T or B lymphocytes. The ultrastructural findings of one case are presented.