Lymphoma - B cell neoplasms - Marginal zone lymphoma, MALT type

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Lymphoma - B cell neoplasms

B cell lymphoma subtypes

Marginal zone lymphoma, MALT type

Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 24 February 2011, last major update February 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

See also MALT-primary sites

Definition
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● Common low grade lymphoma that emulates Peyer's patches of terminal ileum

Epidemiology
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● Associated with Sjogren's syndrome, and possibly other chronic inflammatory diseases of salivary gland like lymphoepithelial sialadenitis (Am J Surg Pathol 2001;25:1546)
● Associated with Hashimoto's thyroiditis, Helicobacter pylori gastritis, Chlamydia psittaci, Campylobacter jejuni, possibly Hepatitis C virus or Borrelia burgdorferi infection

Sites
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● Stomach, bowel, salivary glands, lung, thyroid, lacrimal gland, conjunctiva, bladder, kidney, skin, soft tissue, thymus, breast
● Occasionally bone marrow (20%) and spleen
● GI tract most common (50% of all cases); within GI tract, stomach is most common (85%, Gastroenterology 1992;102:1628)

Clinical features
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● Most common primary extranodal lymphoma; slightly more common in women
● B cell neoplasm of mucosal and non-mucosal extranodal sites that interacts with epithelium and reactive germinal centers
● Usually localized (70%) and possibly curable by surgery, radiation or antibiotics
● Disseminated disease is usually refractory to chemotherapy
● Indolent course; median survival is 8 years; late relapse in 30% at same site or other extranodal sites
● Rare transformation to large cell lymphoma, which has sheets of large cells and may have Reed-Sternberg like cells
● Includes cases previously designated "pseudolymphoma" or extranodal lymphoid hyperplasia
● May be associated with Waldenström macroglobulinemia (Am J Clin Path 2001;116:683)
● Serum paraprotein (M-component) is present in up to 30% cases, particularly those with plasmacytic differentiation (Clin Cancer Res 2004;10:7179)

CD5+ tumors
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● Associated with disseminated lymphoma, often in head and neck, responding poorly to treatment
● Must rigorously exclude other B cell lymphomas
● Case report of 87 year old woman with breast tumor (Hum Pathol 2003;34:1065)

Gross description
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● Multiple lesions are common

Micro description
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● Architectural effacement by atypical centrocyte-like cells (small cleaved follicular cells with abundant cytoplasm), that infiltrate around reactive B cell follicles in a marginal zone distribution with spread into the interfollicular area
● May invade epithelial structures to form lymphoepithelial lesions; cells are at various stages of B cell differentiation including monocytoid B cells, small lymphocytes, plasma cells, centroblasts and immunoblasts in small numbers
● May have follicular colonization of neoplastic cells resembling follicular lymphoma

Micro images
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Low grade

Low grade with transformation and crystalline inclusions

High grade tumors

Positive stains
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● CD19, CD20, CD22, CD79a, surface Ig, cytoplasmic Ig in plasma cell component, bcl-10
● Variable CD11c, variable bcl2, variable monoclonal light chain expression
● Note: plasmacytoid cells may be negative for B cell markers but are strongly immunoreactive for kappa or lambda

Negative stains
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● IgD, CD5, CD10, CD23; usually CD43 and bcl-1

Molecular
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● t(11;18)(q21;q21): API2 and MALT1 (50%): associated with aggressive disease and poor response to antibiotics
● t(14;18)(q32;q21): IgH and MALT1: described in nongastric extranodal MALT lymphomas; indistinguishable from IgH-bcl2 by cytogenetics; associated with other karyotypic abnormalities including various trisomies
● t(1;14)(p22;q32): bcl-10 and IgH (% unknown): inactivates the “pro-apoptotic” bcl-10 protein; associated with advanced MALT
● t(1;2)(p22;p12): bcl-10 and Ig Kappa
● Trisomy 18 is also common; trisomy 3 is present, whole or partial in 26-55%
● Multiple lesions often have 1-3 neoplastic clones (Mod Pathol 2001;14:957)
● Low grade lesions often are bcl6 negative, but have bcl6 mutations by PCR

Differential diagnosis
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● CLL/SLL: CD5+, CD23+
● Follicular lymphoma: CD10+
● Mantle cell lymphoma: CD5+
● Reactive:: lack destructive / infiltrative pattern of extrafollicular B-cells demonstrated by CD21/CD35 (staining follicular dendritic cells)
● Also inflammatory pseudotumor, rhabdomyomas if tumors contain crystalline inclusions (Arch Pathol Lab Med 2000;124:460)

End of Lymphoma - B cell neoplasms > B cell lymphoma subtypes > Marginal zone lymphoma, MALT type

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