MALT Lymphoma: Understanding Diagnosis, Symptoms & Treatment

Extranodal Marginal Zone Lymphoma of Mucosa-Associated Lymphoid Tissue (MALT lymphoma) is a low-grade (indolent) B-cell non-Hodgkin lymphoma arising from post-germinal center memory B cells in lymphoid tissue acquired at mucosal sites. It is the most common gastric lymphoma (~50%) but occurs at any mucosal site.

Common Sites

• Stomach (60–70%) — strongly linked to H. pylori
• Lung, ocular adnexa (orbit/conjunctiva), salivary gland, thyroid, skin, small intestine, liver, breast

Etiology: Infection-Driven Lymphomagenesis

Symptoms (Site-Dependent)

• Gastric: Epigastric pain, early satiety, nausea, weight loss, GI bleeding, B symptoms (fever, night sweats, weight loss >10%).
• Ocular: Proptosis, conjunctival mass, diplopia.
• Pulmonary: Cough, dyspnea, hemoptysis — often incidental on imaging.
• General: Lymphadenopathy rare; B symptoms in advanced stage.

Diagnosis

1. Endoscopy + biopsy (gastric): Multiple biopsies (mucosal + submucosal).
2. Histology: Small lymphocytes with irregular nuclei, centrocyte-like, monocytoid, plasma cell differentiation. Lymphoepithelial lesions (LELs) — pathognomonic.
3. Immunophenotype: CD20+, CD19+, CD79a+, BCL2+, CD5−, CD10−, CD23−, Cyclin D1−.
4. Genetics: t(11;18)(q21;q21) API2-MALT1 (30%, predicts H. pylori resistance); t(1;14), t(14;18) IGH-MALT1; trisomy 3, 18.
5. Staging: CT chest/abdomen/pelvis, PET-CT, bone marrow biopsy, endosonography (EUS).

Treatment by Stage

Site	Associated Pathogen	Mechanism
Gastric	H. pylori	Chronic antigenic stimulation → NF-κB, API2-MALT1 translocation
Ocular adnexa	Chlamydia psittaci	Similar chronic stimulation
Skin	Borrelia burgdorferi	Lyme-associated
Lung	Achromobacter, Pseudomonas	Chronic inflammation
Thyroid	Hashimoto's thyroiditis	Autoimmune lymphoid infiltration

Prognosis

• 5-yr OS: Stage I/II ~95%; Stage III/IV ~70–80%.
• Median survival >10–15 years.
• Transformation to DLBCL: 5–15% (aggressive, treat as DLBCL).

MALT lymphoma is a paradigm of infection-driven cancer—eradication therapy can cure early gastric disease without chemotherapy or radiation.

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Stage	Approach
Gastric, H. pylori+, Stage I/II (IE/IIE)	H. pylori eradication (PPI + 2 antibiotics × 14 d). CR 70–90%. Surveillance endoscopy 3–6 mo.
Gastric, H. pylori− or t(11;18)+	Radiotherapy (30–36 Gy) — excellent local control. Or rituximab ± chemo.
Non-gastric / Stage III/IV	Rituximab ± bendamustine/CHOP; radiotherapy for localized; surgery rarely.
Asymptomatic, low tumor burden	Watch & wait (active surveillance).