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Extranodal marginal zone lymphoma of mucosal- associated lymphoid tissue (MALT lymphoma)

Reviewers: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 26 September 2012, last major update September 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


Definition (WHO):
● An extranodal lymphoma composed of morphologically heterogeneous small B-cells including marginal zone (centrocyte-like) cells, cells resembling monocytoid cells, small lymphocytes, and scattered immunoblasts and centroblast-like cells
● There is plasma cell differentiation in a proportion of cases
● The infiltrate is in the marginal zone of the reactive B-cell follicles and extends into the interfollicular region
● In epithelial tissues the neoplastic cells typically infiltrate the epithelium forming lymphoepithelial lesions


● Develops in background of H. pylori infection or rarely post-transplant (usually low grade, EBV-, mean 7 years after transplant, Am J Surg Pathol 2000;24:100)
● Arises from post-germinal center marginal zone B cells (usually negative for bcl6, CD5 and CD10)
H. pylori chronic infection produces H. pylori reactive T cells, => activation of polyclonal B cells => (over time) emergence of monoclonal B cell population(s), still dependent on T cell activation (now still reversible), => T cell independence (similar to EBV, HTLV-1 models)
● May also arise as oligoclonal proliferations with separate lesions composed of different clones, dominant clones then appear and may disseminate to other lesions (Mod Pathol 2001;14:957)

Clinical description

● Indolent
● When it spreads, tends to involve other mucosal sites such as Waldmeyer’s ring
● 5 year cause-specific survival is 94%; scattered large cells making up 5-10% of tumor cells do not affect prognosis (Am J Surg Pathol 2001;25:95)
● May transform to diffuse large B-cell lymphoma
● The coexistance of MALT lymphoma and diffuse large B-cell lymphoma should not be reported as “high grade MALT” because extranodal marginal zone (MALT) lymphoma is an indolent lymphoma; report as diffuse large B-cell lymphoma with the presence of MALT lymphoma
● May have coexisting GI or GU carcinomas (Am J Surg Pathol 1997;21:505)

Case reports

● 36 year old woman with gastric MALT, thymic MALT and Sjogren’s syndrome (Arch Pathol Lab Med 2000;124:770)
● 56 year old woman with untreated celiac sprue (Case of the Week #127)
● MALT and histiocytic lymphoma of stomach (Am J Surg Pathol 1996;20:1406)


● Antiobiotics for H. pylori gastritis (patients may have positive serology even if H. pylori negative by histology; these patients may also respond to treatment, Mod Pathol 1999;12:1148)
H. pylori eradication therapy produces a long term favorable outcome (Tohoku J Exp Med 2008;214:79)
● Also radiation therapy
● t(11;18)(q21;21) tumors unlikely to respond only to H. pylori eradication

Gross images

Gastric lymphoma

Micro description

● Dense, monotonous population of centrocyte-like cells, often with residual germinal centers and lymphoepithelial lesions (Am J Surg Pathol 1996;20:588)
● May have plasmacytoid differentiation
● Commonly lymphoepithelial lesions (infiltration of glandular epithelium by lymphocytes) or follicular colonization
● Adjacent mucosa has epithelial erosion (61%), intestinal metaplasia (59%), H. pylori (57%), lymphoid follicles (39%), atrophy (37%), atypical regenerative changes (19%), dysplasia (4%, Arch Pathol Lab Med 2000;124:1628)
● Signet-ring epithelial cells are present in 1/3 in superficial lamina propria associated with lymphoid areas, may represent lymphoepithelial lesions (Am J Surg Pathol 1996;20:588)

Micro images

Lymphoepithelial lesion

Various images

Monoclonal light chain staining

Case of the week #127 - stomach nodule




Modified Steiner stain of other areas of stomach

Positive stains

● B cell markers (CD19, CD20, CD79a), CD43 (variable)
● Monoclonal light chain restriction

Negative stains

● CD5 (Am J Surg Pathol 1992;16:130), bcl6, CD10


● t(11;18)(q21;q21): 6-26%
● t(14;18)(q32;q21): 1-5%
● +3: 11%
● +18: 6%

Molecular description

● Gene rearrangement positive, but PCR may be falsely positive as gastritis contains monoclonal B cells (Mod Pathol 1999;12:885, Am J Surg Pathol 2003;27:882)

Differential diagnosis

Lymphoid hyperplasia or other benign process: rare lymphoepithelial lesions, no Dutcher bodies, no atypia, no monoclonality immunohistochemistry

End of Stomach > Lymphoma > Extranodal marginal zone lymphoma of mucosal- associated lymphoid tissue (MALT lymphoma)

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