MALT lymphoma

Mucosa-associated lymphoid tissue (MALT) lymphoma, sometimes shortened to MALToma, is a type of low-grade extranodal lymphoma.

Terminology

In the 5^th edition of the WHO classification of haematolymphoid tumours, it is a mature B-cell neoplasm termed extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. This is a separate entity from "nodal marginal zone lymphoma", fundfound in the marginal zone of the germinal follicles of a lymph node.

Epidemiology

MALT lymphoma represents ~7.5% of non-Hodgkin lymphomas. The average age of presentation is 60 years with a slight female predominance ¹. Prevalence is estimated at 2 per 100,000 ⁷. 

Clinical presentation

Clinical presentation depends on the affected organ. B-type symptoms are rare ^1,3.

Pathology

MALT lymphomas arise in epithelial tissues where lymphoid cells are not usually found. Chronic infection/inflammation has been implicated in the pathogenesis, for example, Helicobacter pylori infection with gastric MALT lymphoma, and Sjögren syndrome with salivary gland MALT lymphoma ^1,3. Less than 10% transform from low-grade to high-grade disease ⁴.

MALT lymphoma can localise throughout the entire body ^1,4:

• stomach: most common; 33-50% (see: gastric lymphoma)

  • associated with H. pylori infection in 90% of cases ⁷

• intestine: ~5%

  • possible association with coeliac disease ⁶

• salivary glands: associated with Sjögren syndrome

• skin

• dura (see: MALT lymphoma of the dura)

• thyroid: associated with Hashimoto thyroiditis ⁵

• orbit (see: orbital lymphoma)

• breast

• lung and upper airways (see: BALT lymphoma)

• kidney

• liver

• rectum

• prostate

Metastases to other sites including lymph nodes and bone marrow are not uncommon. 

Radiographic features

Imaging features of MALT lymphoma depend on which organ is affected. 

Treatment and prognosis

MALT lymphoma is considered an indolent disease with a good prognosis. Treatment should be tailored to the affected organ and may consist of surgery, chemotherapy, and/or radiation therapy ². Antibiotics are used to treat gastric MALT lymphoma; there is a lack of evidence for their use in treating non-gastric MALT lymphoma ⁷.

See also

• marginal zone lymphoma