SPLENIC MARGINAL ZONE CELL LYMPHOMA - AN IMMUNOPHENOTYPIC AND MOLECULAR STUDY OF 5 CASES

Splenic marginal zone cell lymphoma (SMZCL) is a recently described cl inicopathologic entity, that is reported to overlap with splenic B-cel l lymphoma with villous lymphocytes. The authors describe the clinicop athologic, immunophenotypic, and molecular findings in Eve cases of SM ZCL. There were two males and three females, with a mean age of 68.4 y ears, who presented with peripheral blood cytopenias and splenomegaly. One patient had an absolute lymphocytosis with many villous lymphocyt es. With clinical follow-up of 9 to 37 months, two patients are alive and three patients died of unrelated causes. Splenectomy was done in e ach patient and the spleens were large, 970-2,400 g. Histologically, t he SMZCLs preferentially replaced the marginal and mantle zones with p artial or complete replacement of germinal centers in the white pulp. The neoplastic cells were predominantly small to medium in size with o val or slightly irregular nuclei and relatively abundant pale or eosin ophilic cytoplasm. Immunophenotypic studies demonstrated that the neop lastic cells expressed monotypic immunoglobulin, IgD in four tumors, p an-B-cell antigens, and bcl-2. The tumor cells were negative for the C D2, CD3, CD5, CD10, CD11c, CD25, CD35, CD38, CD45RO, and CD68 antigens , and tartrate-resistant acid phosphatase. Southern blot hybridization revealed immunoglobulin gene rearrangements in all tumors. The major breakpoint region of the bcl-2 gene and the T-cell receptor beta chain gene were in the germline configuration. Polymerase chain reaction st udies did not identify the t(14;18) or t(11;14). All cases were negati ve for p53 protein and single-stranded conformational polymorphism ana lysis for p53 gene mutations was negative. Our results support the con cept that SMZCL is a clinically indolent, low grade B-cell lymphoma th at probably arises from splenic marginal zone lymphocytes.