Extranodal Marginal Zone Lymphoma of Mucosal Associated Lymphoid Tissue (MALT Lymphoma)

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) involves extra nodal tissue and shows infiltration of the marginal zones and inter follicular regions.

Gastric MALT is associated with H. pylori infection in up to 90% of cases.
MALT in the thyroid has been associated with Hashimoto’s thyroiditis (~20% of cases).
Ocular MALT lymphomas have been associated with various infections.

Immunophenotype

Marker	Comment
CD3	Negative
CD19	Positive
CD20	Positive
CD79a	Positive
CD23	Negative
CD5	Negative
CD10	Negative
CD43	30-50% may be positive (not significant in the terminal ileum)
Bcl-2	Positive
Bcl-6	Negative
CD21	Highlights disrupted networks of FDCs.
Ki-67	Low
CyclinD1	Negative
CD138	Highlight plasma cell component, which may be studied with kappa/lambda markers to prove monoclonality.

References

Parker, A., et. al. “Best Practice in Lymphoma Diagnosis and Reporting.” British Committee for Standards in Haematology, Royal College of Pathologists. April, 2010.