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

Topic Completed: 1 September 2012

Minor changes: 21 January 2020

Copyright: 2003-2019,, Inc.

PubMed Search: gastric MALT lymphoma

Elliot Weisenberg, M.D.
Page views in 2019: 16,091
Page views in 2020 to date: 9,139
Cite this page: Weisenberg E. Extranodal marginal zone lymphoma of mucosal associated lymphoid tissue (MALT lymphoma). website. Accessed July 7th, 2020.
Definition / general
  • WHO definition:
    • 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 features
  • 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
  • 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
Microscopic (histologic) 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)
Microscopic (histologic) images

Contributed by Andrey Bychkov, M.D., Ph.D.,
Kameda Medical Center


Case of the Week #127

Stomach nodule




Modified Steiner stain of
other areas of stomach

Images hosted on other servers:

Lymphoepithelial lesion

Various images

Monoclonal light chain staining

Positive stains
  • B cell markers (CD19, CD20, CD79a), CD43 (variable)
  • Monoclonal light chain restriction
Molecular / cytogenetics description
Differential diagnosis
  • Lymphoid hyperplasia or other benign process: rare lymphoepithelial lesions, no Dutcher bodies, no atypia, no monoclonality immunohistochemistry
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