Splenic involvement by aggressive malignant lymphomas of B-cell and T-cell types. A morphologic and immunophenotypic study.

To determine whether there are any consistent morphologic differences between B-cell and T-cell aggressive non-Hodgkin's lymphomas of the spleen, the authors analyzed 16 spleens involved by mixed cell (1 case) or large cell (15 cases) lymphomas. Immunologic data were derived from cell suspensions or frozen tissue in each case. Five cases had a T-cell phenotype, and 11 were B-cell. Morphologic features favoring a T-cell phenotype included epithelioid histiocytic reactions, confinement of the lymphomas to the splenic T-zones (periarteriolar lymphoid sheath and marginal zone), and clear cell or polymorphous cytologic features. Features favoring a B-cell phenotype included multiple discrete nodules in the white pulp, large coalescent tumor nodules in association with small lymphocytic lymphoma, and large non-cleaved or immunoblastic plasmacytoid cytologic characteristics. Four cases were unusual because most neoplastic large cells were distributed diffusely or formed only small aggregates in the red pulp without definite tumor masses or nodules involving the white pulp. Because of this distribution and the frequently encountered erythrophagocytosis by benign-appearing histiocytes, these cases resembled malignant histiocytosis. A T-cell phenotype was predicted for all four cases; however, only one case, a lymphoma with polymorphous cytologic characteristics, was of T-cell lineage. The other three cases were of B-cell lineage. The authors' results indicate that in most instances the B-cell or T-cell nature of aggressive splenic lymphomas is predictable from the distributional and cytologic features. As in lymph nodes, there are cases for which the morphologic characteristics of B-cell and T-cell lymphomas are indistinguishable.