Lymphoma & related disorders
Mature B cell neoplasms
Small B cell lymphomas with lymphoplasmacytic differentiation / marginal zone lymphomas
MALT-marginal zone
Author: Nikhil Sangle, M.D.
Topic Completed: 1 February 2011
Minor changes: 18 December 2020
Copyright: 2001-2021, PathologyOutlines.com, Inc.
PubMed Search: marginal zone lymphoma MALT-type
Table of Contents
Definition / general | Epidemiology | Sites | Clinical features | CD5+ Tumors | Gross description | Microscopic (histologic) description | Positive stains | Negative stains | Molecular / cytogenetics description | Differential diagnosisCite this page: Sangle N. MALT-marginal zone. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lymphomaMALT.html. Accessed January 22nd, 2021.
Definition / general
- Common low grade lymphoma that emulates Peyer patches of terminal ileum
Epidemiology
- Associated with Sjogren syndrome, and possibly other chronic inflammatory diseases of salivary gland like lymphoepithelial sialadenitis (Am J Surg Pathol 2001;25:1546)
- Associated with Hashimoto thyroiditis, Helicobacter pylori gastritis, Chlamydia psittaci, Campylobacter jejuni, possibly Hepatitis C virus or Borrelia burgdorferi infection
Sites
- 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
- Most common primary extranodal lymphoma; slightly more common in women
- B cell neoplasm of mucosal and nonmucosal 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
- 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
- Multiple lesions are common
Microscopic (histologic) description
- 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
Positive stains
Molecular / cytogenetics description
- 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): BCL10 and IgH (% unknown): inactivates the "pro-apoptotic" BCL10 protein; associated with advanced MALT
- t(1;2)(p22;p12): BCL10 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
- 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)
