Colon tumor
Lymphoma and hematopoietic lesions
MALT lymphoma

Topic Completed: 1 February 2012

Revised: 12 June 2019

Copyright: 2003-2019,, Inc.

PubMed Search: MALT [title] lymphoma colon

Page views in 2018: 1,330
Page views in 2019 to date: 1,502
Cite this page: Singh C. MALT lymphoma. website. Accessed November 20th, 2019.
Definition / general
  • Rare in colon
  • Usually adults
  • Often relapses but usually only in GI tract
Case reports
Gross images

Images hosted on other servers:

flat elevated tumor with slight depression

Microscopic (histologic) description
  • Small atypical lymphocytes with irregular nuclei, lymphoepithelial lesions
  • Reactive germinal centers and plasmacytic cells are common

Can be graded as:
  • Grade 0: Normal - plasma cells in lamina propria, no lymphoid follicles
  • Grade 1: Chronic active inflammation - lymphocyte clusters in lamina propria, no follicles and no lymphoepithelial lesions
  • Grade 2: Chronic active inflammation with florid lymphoid follicle formation - prominent follicles with surrounding mantle zone and plasma cells, no lymphoepithelial lesions
  • Grade 3: Suspicious lymphoid infiltrate in lamina propria, probably reactive - follicles surrounded by lymphocytes that infiltrate diffusely in lamina propria and / or epithelium
  • Grade 4: Suspicious lymphoid infiltrate in lamina propria, probably lymphoma - follicles surrounded by centrocyte-like, marginal zone cells that infiltrate diffusely in lamna propria and epithelium
  • Grade 5: Marginal zone (MALT) lymphoma - dense diffuse infiltrate of centrocyte-like, marginal zone cells in lamina propria with prominent lymphoepithelial lesions

Post therapy grading:
  • Complete histologic remission:
    • Absent or scattered plasma cells and small lymphoid cells in the lamina propria
    • No lymphoepithelial lesions
    • Normal or empty lamina propria and / or fibrosis

  • Probable minimal residual disease:
    • Aggregates of lymphoid cells or lymphoid nodules in the lamina propria and / or muscularis mucosa and / or submucosa
    • No lymphoepithelial lesions
    • Empty lamina propria and / or fibrosis

  • Responding residual disease:
    • Dense, diffuse or nodular extending around glands in the lamina propria
    • Lymphoepithelial lesions, may or may not be present
    • Focal empty lamina propria and / or fibrosis

  • No response:
    • Dense, diffuse or nodular lymphoid infiltrates
    • Lymphoepithelial lesions, may or may not be present
    • No changes in the stroma
Microscopic (histologic) images

Images hosted on other servers:

showing diffusely
positive staining for L26

Lymphoma cells
infiltrated into
mucosal and
submucosal layers

Molecular / cytogenetics description
  • Usually trisomy 3 or 18, less commonly t(1;14)(p22;q32, Gut 2006;55:1581 or t(11;18)(q21;q21) in 15% (Mod Pathol 2003;16:1232)
  • T(11;18) produces API2-MALT1 fusion gene; these tumors usually occur in males and are larger with more advanced stage
  • API2-MALT1 negative tumors usually occur in females
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