Primary nodal marginal zone lymphomas of splenic and MALT type

The existence of primary nodal marginal zone lymphomas (MZL) is controversi al, as is their relationship to putative extranodal counterparts. Most noda l lymphomas with monocytoid B cell/marginal zone differentiation exhibit th e morphologic and immunophenotypical characteristics of extranodal MALT-lym phomas. Splenic marginal zone lymphoma (SMZL) is also of putative marginal zone derivation, but it differs immunophenotypically from MALT lymphoma. To clarify the relationship between nodal and extranodal MZLs and to investig ate the possible existence of a nodal variant of SMZL, 36 MZL initially con sidered to be primary nodal neoplasms were examined. Other low-grade lympho mas with marginal zone differentiation were excluded (small lymphocytic lym phoma/chronic lymphocytic leukemia [SLL/CLL], follicular lymphoma, and mant le cell lymphoma). Six nodal MZLs showed morphologic and phenotypic charact eristics similar to those of SMZL, whereas 30 tumors were more similar to M ALT-type lymphomas. The six tumors with SMZL features showed a polymorphic infiltrate surrounding residual germinal centers with absent or very attenu ated mantle cuffs. These lymphomas were IgD positive (6/6) but cyclin D1 (0 /5), CD5 (0/6), and CD23 (0/6) negative. Five of these patients came for tr eatment in stage I or II. No patient manifested splenomegaly, peripheral bl ood, and/or bone marrow infiltration either at diagnosis or during follow-u p. Lymph nodes from 30 patients with MALT-type features showed a perisinuso idal and perivascular infiltration of monocytoid/centrocytoid cells and res idual germinal centers with a relatively well-preserved mantle cuff. The ne oplastic cells were negative for IgD (0/17), cyclin DI (0/8), and CD5 (0/12 ). Seven of 16 (44%) patients with a detailed history and clinical follow-u p had evidence of extranodal lymphoma. These observations suggest that most nodal B cell lymphomas with marginal zone differentiation are of the MALT type and that they are frequently associated with an extranodal component I n addition, a primary nodal counterpart of splenic MZL also exists, and may occur in the absence of splenomegaly.