Cutaneous marginal zone lymphomas have distinctive features and include 2 subsets.
Cutaneous marginal zone lymphomas (CMZL) were segregated in the WHO/EORTC consensus classification but grouped with other MALT lymphomas in the subsequent WHO classification. It has been suggested, however, that CMZL have distinctive features and might include 2 subsets. To address these issues, the clinicopathologic, phenotypic and, when possible, genotypic features of 29 CMZL with plasmacytic differentiation were assessed. The monotypic plasma cells had class-switched heavy chain expression in 22 cases, technically inadequate staining in 1 case (included with class-switched cases for analysis) and 6 were IgM. The class-switched cases had a predominance of T cells in 22 out of 23 cases with a CD4:CD8>1 in 15 out of 16 cases, usually showed nodules and scattered small B cells often with IgD apparently nonneoplastic follicles, lacked CXCR3 B-cell expression, never showed a totally diffuse growth pattern, often had prominent mast cells, and lacked known extracutaneous involvement. The IgM cases showed a predominance of B cells in 5 out of 6 (P=0.0003), a diffuse proliferation of CD20 B cells in all (P<0.0001), CXCR3+ B cells in 2 out of 5 (P<0.04), and extracutaneous disease in 3 out of 6 (P<0.008). CD21 usually disrupted follicular dendritic meshworks were seen in 9 out of 12 class-switched and 5 out of 5 IgM cases. CD123 plasmacytoid dendritic cells, PD1+ T follicular helper cells, CD25 or FOXP3+ regulatory T cells, and TIA1/granzyme B cytotoxic cells were never numerous. Only 1 out of 14 tested cases showed a low-level clonal/oligoclonal T cell receptor γ gene rearrangement. These findings support the presence of 2 types of cutaneous MALT lymphomas with the class-switched cases being the most distinctive but still sharing significant features with MALT lymphomas from other sites, specifically an extranodal extramedullary CD5-, CD10- indolent small B cell lymphoma with plasmacytic differentiation, frequent benign follicular structures, and not fulfilling the criteria for any other well-defined lymphoma.
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
James T
JT
Edinger
Jeffrey A
JA
Kant
Steven H
SH
Swerdlow
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D005260:Female; D006801:Humans; D017578:Immunoglobulin Class Switching; D007136:Immunoglobulins / Q000235:genetics / Q000378:metabolism; D018442:Lymphoma, B-Cell, Marginal Zone / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D054367:Receptors, CXCR3 / Q000378:metabolism; D012878:Skin Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor; C515187:CXCR3 protein, human; D007136:Immunoglobulins; D054367:Receptors, CXCR3