• Clinical science

MALT lymphoma (Extranodal marginal zone lymphoma)

Abstract

Mucosa-Associated Lymphoid Tissue (MALT) lymphoma (also called MALToma or extranodal marginal zone lymphoma) is a B-cell non-Hodgkin lymphoma (NHL) that typically affects elderly patients in the 7th and 8th decades. MALTomas can be categorized according to their location as either gastric or nongastric. Gastric MALTomas are frequently associated with Helicobacter pylori (H. pylori) infection, whereas nongastric MALTomas are rather associated with autoimmune conditions (e.g., Sjögren syndrome, Hashimoto's thyroiditis). MALTomas typically present with nonspecific symptoms (e.g., fatigue, weight loss) and an unremarkable physical exam. Diagnosis is based on histopathology and immunohistochemistry. In the case of gastric MALTomas, a biopsy should be performed by upper gastrointestinal (UGI) endoscopy. Imaging techniques such as computed tomography (CT) are used for staging purposes. Treatment depends on the type of MALToma: Gastric MALTomas, for example, are treated in most cases with the eradication of the underlying H. pylori infection, whereas nongastric MALTomas are treated with radiation, chemotherapy, and surgery.

Epidemiology

  • Approx. 5% of NHLs are due to MALTomas
  • Peak incidence: 7th and 8th decades

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

MALTomas show an association with chronic immune stimulation (bacterial, autoimmune)! References:[2][3][1]

Clinical features

  • Symptoms depend on the affected organ
  • Gastric MALTomas
  • Non-gastric MALTomas:
    • Salivary MALToma: parotid enlargement
    • Thyroid MALToma: may present with compression symptoms (e.g., dysphagia, hoarseness)

References:[1][4]

Diagnostics

General approach

  • Blood analysis: anemia
  • Histopathology and immunohistochemistry
    • Thick infiltrates of small to medium-sized lymphoid cells
    • Granulation tissue, ulcerations
    • Immunologic phenotyping: markers of B-cell lymphoma (e.g., CD20)
      • Positive for CD 19/20/22, negative for CD 5/10/23
      • Low-grade MALTomas: BCL-2 positive
      • Intermediate-grade MALTomas: BCL-2 negative
      • Ki-67 positive
  • Imaging: CT, MRI, PET-CT for tumor staging
  • Staging: according to the Ann Arbor staging for NHL

Gastric MALToma

  • Additionally, upper gastrointestinal (UGI) endoscopy
  • Imaging: CT scan of the chest and abdomen with IV contrast for staging

References:[1][5]

Treatment

Gastric MALTomas

  • First-line: H. pylori eradication therapy
    • Should be performed even if patient tests negative
    • Eradication of H. pylori is curative in up to 90% of low-malignant gastric MALTomas
  • If H. pylori eradication therapy fails → radiotherapy or chemotherapy
    • Radiotherapy is preferred if MALToma is found within one area that can be targeted with a single radiation field.
    • Chemotherapy is performed with either chlorambucil or rituximab alone, or in combination.
  • Surgery: gastric resection only necessary if complications (e.g., perforation, bleeding, obstruction) occur.

Nongastric MALToma

  • Depends on the exact type and staging
  • Treatment options include : radiation, chemotherapy, surgery for local diseases

References:[5][1]