Splenic marginal zone cell lymphoma: report of an indolent variant without massive splenomegaly presumably representing an early phase of the disease.

Splenic marginal zone (MRZ) cell lymphoma is a recently described neoplasm arising in a unique compartment of splenic white pulp, producing massive splenomegaly and spreading to bone marrow and distant lymph nodes. We report three cases of splenic lymphoma that morphologically and immunohistochemically appear to originate from MRZ cells that presented as indolent neoplasms involving the spleen but with no or only moderate enlargement of the organ, presumably representing an early clinical stage of this disorder. Despite the evidence of involvement of the liver in one case, lymph nodes and bone marrow proved to be uninvolved. Histologically, the three spleens showed similar features, being characterized by the involvement of white pulp follicles and periarteriolar lymphoid sheaths by medium-sized lymphoid cells with slightly irregular nuclei and ample cytoplasm. Immunohistochemically, all the specimens expressed a series of B-lineage markers that, in contrast to specimens of monocytoid B cell lymphoma (MBCL) and hairy cell leukemia (HCL) studied for comparison, did not react with KiB3, LN1, and DBA.44 monoclonal antibodies.