What is MALT?

Mucosa-associated lymphoid tissue (MALT) is scattered along mucosal linings to protect the body from an enormous quantity and variety of antigens. The tonsils, Payer patches within the small intestine, and the vermiform appendix are examples of MALT.
MALT includes

  • Gut-associated lymphoid tissue (GALT)
  • Bronchial/tracheal-associated lymphoid tissue (BALT)
  • Nose-associated lymphoid tissue (NALT)
  • Vulvovaginal-associated lymphoid tissue (VALT).

What is MALToma?

MALToma is a B cell lymphoma arising from the MALT. It is the most common primary GI lymphoma worldwide. NHL accounts for 2-3% of all malignancies, and MALTomas comprise approximately 5% of all NHLs.

What are the predominant sites of MALT-lymphoma?

  • GI-Tract- Stomach (75%), small bowel (9%), Ileocaecal (7%), Multifocal (6%)
    Rectum (2%), Colon (1%)
  • Lung
  • Salivary Glands
  • Ocular adnexa
  • Skin

Why is MALToma a malignant condition?

  • Monoclonality
  • Non-random chromosomal aberration
  • Histologic transformation to high-grade lymphoma
  • Metastasis to lymph nodes/bone marrow.

Gastric MALTomas

Discuss the pathogenesis of gastric MALToma?

H. Pylori infection has been definitively established as a cause of MALTomas. 90% of MALToma pts are infected with H. Pylori.

  • Infection by H Pylori
  • Increase in MALT tissue
  • Additional genetic mutations
  • Malt lymphoma

What are the clinical features of gastric MALToma?

  • Median age is 63 years with equal gender distribution
  • Symptoms- epigastric pain, dyspepsia, nausea and vomiting and gastric bleeding. B symptoms can occur.
  • The duration of symptoms preceding the diagnosis may range from a few days to six years.

How is MALToma diagnosed?

MALToma is usually diagnosed at endoscopy. MALToma can occur anywhere in the stomach. The most common site is antrum (41%) or multifocal (33%).
The endoscopic findings are erythema, erosions or ulcers. A mass lesion on OGD is unusual.

Discuss the staging investigations for gastric MALToma?

  • Baseline bloods-LDH, B2 microglobulin (both could be elevated)
  • OGD- with multiple biopsies from all the visible lesions & the non-involved areas with complete mapping of the organ
  • CT Chest/Abdomen/pelvis
  • Bone marrow biopsy
  • EUS- for evaluation of depth of invasion and presence of perigastric lymph nodes. A deep infiltration of the gastric wall is associated with a higher risk of lymph node involvement and a lower response rate with antibiotic therapy alone.

Regardless of the presentation site- all the above diagnostic studies should be done.

Discuss the staging system for MALToma?
The best staging system is still controversial. Options are;

  • Modified Blackledge staging system- recommended by International workshop held in Lugano, Switzerland.
  • When EUS is available- TNM can also be employed
  • Ann Arbor
Lugano staging system TNM Ann Arbor stage Tumour extension
Stage I Confined to GI tract T1N0M0
Mucosa, submucosa
Muscularis propria
Stage II Extending into abdomen
II1- local nodal involve.
II2- distant nodal involve.
Perigastric nodes
More distant nodes
Stage III Penetration of serosa to involve adjacent organs T4N0M0 IE Invasion of adjacent structures
Stage IV Disseminated extranodal or concomitant supradiaphragmatic involvement T1-4N3M0
Lymph nodes on both sides of diaphragm or distant metastasis

Discuss the treatment of gastric MALToma?

Optimal therapy remains to be determined due to lack of controlled trials. However, the prognosis is excellent with overall survival rates of 80% to 95% at 5 years.

H. Pylori positive and localised disease (stage IE)

  • HP eradication as sole therapy leads to durable remissions in 60-100%. This approach has been validated extensively, with more than 20 reported studies. Any of the highly effective antibiotic regimens proposed can be used. Thus far, no regimen has been proven to be superior in inducing lymphoma remissions. A second-line anti- Helicobacter therapy with different antibiotics may be needed in some instances.
  • Breadth test 2 months after treatment to confirm eradication
  • OGD with multiple biopsies every 6m for 2 years, then yearly to monitor the histologic regression.
  • B cell clonality often persists (in upto 50%) following successful therapy to eradicate HP or following treatment with radiation therapy alone unlike successful treatment with chemoradiotherapy.The ultimate significance of persistent clonality in this setting is unclear. Histologic evaluation of repeated biopsies remains the fundamental follow up procedure despite the reproducibility problems. Whether the persistence of PCR detected B-cell monoclonality is associated with a higher risk of lymphoma relapse remains to be determined.
  • Remission may take up to a year after HP eradication. So it may be worthwhile waiting 12 months before considering further therapy.

H. Pylori negative, failed antibiotic treatment, non gastric locations or extensive disease (IIE-IV) or extensive mucosal disease.

No definite guidelines exist, as there are no published randomized studies. A choice can be made between conventional therapeutic modalities.

  • The standard of care for localised disease (HP negative or failed antibiotic treatment) is radiation therapy (30Gy in 4 weeks). More than 90% long term disease-free survival.
  • Surgery was once the cornerstone, but the role is limited at present. As MALToma is a multifocal disease, a total gastrectomy will be needed. This is associated with significant morbidity.
  • Systemic disease; Chemotherapy for MALTomas has not been studied extensively. Historically, the chemotherapy used for low-grade NHLs has been used. HP eradication should be used anyways in all cases

What is the prognosis?

MALTomas are indolent neoplasms with a fairly good prognosis. Gastric MALTomas have a stage-dependent prognosis. The cure rate may be as high as 90% for stage IE disease and is approximately 30-40% for extensive stage IIIE or IVE disease.

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