MALT lymphoma

Mucosa-associated lymphoid tissue (MALT) lymphoma is an indolent (low-grade) mature B-cell lymphoma; however, high-grade histologic transformation can occur.

Median age at diagnosis is approximately 67 years.

MALT lymphoma develops at extranodal sites and is commonly associated with autoimmune disease and chronic infection.

The stomach is the most commonly affected site (gastric MALT lymphoma), and is strongly associated with chronic Helicobacter pylori infection. Other sites that are commonly affected include the ocular adnexa, lung, and salivary/parotid glands.

Diagnosis is based on history, physical exam, imaging studies, and biopsy (with histopathologic, immunophenotypic, and genetic evaluation).

Management is based on the involved site (gastric or nongastric), disease stage (localized or advanced), and symptoms. Treatment options include antibiotics (for gastric MALT lymphoma), radiation therapy, immunotherapy (e.g., rituximab), chemotherapy, and surgery.

MALT lymphoma (also known as extranodal marginal zone lymphoma [EMZL] of MALT) is a mature B-cell non-Hodgkin lymphoma.[1]WHO Classification of Tumours Editorial Board. Haematolymphoid tumours: WHO classification of tumours. 5th ed. (vol. 11)​. Lyon (France): International Agency for Research on Cancer; 2022.​​[2]Campo E, Jaffe ES, Cook JR, et al. The International Consensus Classification of Mature Lymphoid Neoplasms: a report from the Clinical Advisory Committee. Blood. 2022 Sep 15;140(11):1229-53. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9479027 http://www.ncbi.nlm.nih.gov/pubmed/35653592?tool=bestpractice.com ​ It is a marginal zone lymphoma (MZL).[3]Alaggio R, Amador C, Anagnostopoulos I, et al. The 5th edition of the World Health Organization Classification of haematolymphoid tumours: lymphoid neoplasms. Leukemia. 2022 Jul;36(7):1720-48. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9214472 http://www.ncbi.nlm.nih.gov/pubmed/35732829?tool=bestpractice.com

Other MZLs include splenic MZL (SMZL) and nodal MZL (NMZL). See Non-Hodgkin lymphoma for more information on SMZL and NMZL.

MALT lymphoma develops at extranodal sites. The stomach is the most commonly affected site (known as gastric MALT lymphoma), but any extranodal site can be affected.[4]Zucca E, Arcaini L, Buske C, et al. Marginal zone lymphomas: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2020 Jan;31(1):17-29. https://www.doi.org/10.1016/j.annonc.2019.10.010 http://www.ncbi.nlm.nih.gov/pubmed/31912792?tool=bestpractice.com

MALT lymphomas are composed of morphologically heterogenous small B cells, including marginal zone cells, cells resembling monocytoid cells, small lymphocytes, and scattered immunoblasts and centroblast-like cells.[5]Jaffe ES, Harris NL, Stein H, et al, eds. World Health Organization classification of tumors. Pathology and genetics: tumors of haemopoietic and lymphoid tissues. Lyon, France: IARC Press; 2008.​ Plasmacytic differentiation occurs in some patients. Neoplastic cells are located in the marginal zone of reactive B-cell follicles and extend into the interfollicular region. Lymphoepithelial lesions develop in epithelial tissues due to infiltration of the epithelium with neoplastic cells.[5]Jaffe ES, Harris NL, Stein H, et al, eds. World Health Organization classification of tumors. Pathology and genetics: tumors of haemopoietic and lymphoid tissues. Lyon, France: IARC Press; 2008.

[Figure caption and citation for the preceding image starts]: MALT lymphoma has a polymorphous lymphoid infiltrate that can include small lymphocytes, monocytoid B cells, centrocyte-like cells and cells with plasmacytoid differentiation. Scattered immunoblasts and centroblast-like cells may also be seenHollie N, et al. J Clin Pathol. 2020; 73: 378-83; used with permission [Citation ends].