Professional Reference articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
The body's immune system is made up of a number of masses of lymphoid tissue or organs, as well as circulating leukocytes that originate from the bone marrow. The main lymphoid organs are:
- Bone marrow, thymus, tonsils, spleen and lymph nodes
- Mucosa-associated lymphoid tissue (MALT)
- Gut-associated lymphoid tissue (GALT)
- Bronchus-associated lymphoid tissue (BALT)
- Skin-associated lymphoid tissue (SALT)
MALT lymphoma is a subtype of non-Hodgkin's lymphoma with it's own specific pathology, histology and clinical features. It is distinct because it involves lymphoid proliferation in mucosa-associated lymphoid tissue (MALT) rather than lymph nodes.
Indolent B-cell lymphomas that are supposed to derive from the marginal zone (marginal zone lymphomas) include three specific entities: extranodal marginal zone lymphoma or mucosa-associated lymphatic tissue (MALT) lymphoma, splenic marginal zone lymphomas (SMZLs), and nodal marginal zone lymphomas (NMZLs).
MALT lymphomas follow a different course to nodal B-cell lymphomas. They tend to remain localised for longer, lack poor prognostic features and have a higher five-year survival rate. MALT lymphomas can be divided into:
- Gastric: the most common type and associated with Helicobacter pylori infection.
- Non-gastric: most often in the head and neck, lung and eye. Non-gastric MALT lymphomas are not associated with H. pylori infection.
- MALT can develop in nearly every organ as a result of chronic infection or an autoimmune process. If there is prolonged lymphoid proliferation, a malignant clone can emerge and a MALT lymphoma could follow.
- Certain infections have been associated with MALT lymphomas:
- There is H. pylori infection in 85-90% of gastric MALT lymphomas.
- Chlamydophila psittaci has been identified as a possible causative agent in ocular adnexal lymphomas.
- Borrelia burgdorferi infection has been linked to skin MALT lymphomas.
- Campylobacter jejuni has been linked to small bowel MALT lymphomas.
- There is also a possible link between hepatitis C and HIV and MALT lymphomas.
- Autoimmune diseases such as Hashimoto's thyroiditis and Sjögren's syndrome have also been linked to MALT lymphomas in the thyroid and salivary glands.
- There are certain karyotypic abnormalities associated with MALT lymphoma. A t(11;18)(q21;q21) translocation is a characteristic cytogenetic abnormality in patients with MALT lymphomas.
- Extranodal marginal zone lymphomas of MALT type represent about 7% of all non-Hodgkin’s lymphomas in the Western world and can arise at any extranodal site.
- At least one third of them present as a primary gastric lymphoma, which in approximately two thirds of cases is associated with a chronic H. pylori infection.
- It is most likely to present in the sixth decade.
- Females are affected more than males.
- These depend on the site involved:
- Gastric MALT lymphomas may present with dyspepsia.
- Nonspecific symptoms include fatigue, low-grade fever, nausea, constipation, weight loss and anaemia.
- Recurrent respiratory tract infections.
- Orbital MALT lymphomas may present with blurred vision and visual field defects.
- MALT lymphoma usually follows an indolent course. It can remain localised for long periods.
- Rarely, there is transformation to a more aggressive form of lymphoma.
- Relapses of MALT lymphoma may be late and lifelong observation may be required.
- General assessment: FBC, renal function tests, electrolytes, LFTs.
- Phenotyping of circulating lymphocytes, bone marrow lymphocytes or biopsy specimens.
- Imaging studies for disease staging:
- Barium contrast studies of the upper and lower gastrointestinal tract.
- CT scan and MRI scan.
- Bone marrow aspiration.
Management is different for gastric and non-gastric MALT lymphomas.
- Treatment with a proton pump inhibitor (PPI) and antibiotics to eradicate H. pylori is the main treatment for most gastric MALT lymphomas, which are often low-grade and remain localised for several years. Treatment with chemotherapy, surgery or radiotherapy has not been demonstrated to be superior to antibiotic treatment.
- Treatments for non-gastric MALT lymphomas include radiotherapy, chemotherapy, monoclonal antibodies and surgery.
- Rituximab alone or in combination with chemotherapy is reported to provide high response rates and has been advocated for those with disseminated or recurrent disease.
Surgery has only a limited role in treatment. Surgery for non-gastrointestinal MALT lymphoma is usually restricted to excisional biopsies. Partial or total gastrectomy is associated with considerable morbidity and is rarely necessary.
Specific types of mucosa-associated lymphoid tissue lymphoma
Gastric MALT lymphoma
- Associated with: H. pylori infection.
- Presenting features: dyspepsia, epigastric discomfort, gastric bleeding. Systemic symptoms (night sweats, weight loss, fever, lethargy) and bone marrow involvement are less common. Most are localised to the stomach at presentation.
- Diagnosis: endoscopy and gastric biopsy. There are characteristic histological features.
- Eradication of H. pylori with antibiotics and a PPI or H2-receptor antagonist can lead to a complete remission of gastric MALT lymphoma in between 65-70% of cases and is first-line treatment for early-stage disease.[1, 11]
- If H. pylori status is negative, eradication treatment may not work.
- Close follow-up using endoscopy is needed after eradication treatment to ensure a complete response.
- If there is locally-advanced or high-grade disease, chemotherapy, monoclonal antibody treatment with rituximab, or radiotherapy should be added to eradication treatment.
- Surgery is reserved for refractory disease, as gastric preservation is preferred if possible.
- Current clinical trials involving these different treatment modalities are underway.
- Prognosis: the overall five-year survival and disease-free survival rates are as high as 90% and 75%, respectively.70-80% of patients reveal complete remission of MALT lymphoma following successful eradication of H. pylori.
Salivary gland MALT lymphoma
- Associated with: Sjögren's syndrome.
- Clinical features: involvement of salivary glands with MALT lymphoma is rare. May involve all salivary glands either initially or subsequently in 30% of patients.
- Treatment: radiotherapy is the only treatment modality that improves disease-free survival.
- Prognosis: recurrences may occur in up to 35% of patients at five years but survival is not affected.
Ocular adnexa and lacrimal gland MALT lymphoma
- Associated with: C. psittaci has been associated with the pathogenesis of ocular adnexal lymphomas in some parts of the world.
- Clinical features: painless conjunctival injection, photophobia, orange/salmon-pink masses in the fornices. The most common manifestation site of ocular MALT lymphoma is the conjunctiva.
- Treatment: radiotherapy. Cataract and dry eyes are complications of this.
- Prognosis: five-year survival rate 91%.
Lung MALT lymphoma
- Associated with: autoimmune diseases (Sjögren's syndrome, rheumatoid arthritis).
- Clinical features: arises from bronchus-associated lymphoid tissue (BALT). 40% are asymptomatic and present with a solitary pulmonary nodule on CXR. There may be cough, dyspnoea, haemoptysis, fever, weight loss. Can spread throughout the lung and to other MALT.
- Treatment: surgery (if localised), chemotherapy, radiotherapy.
- Prognosis: usually has an indolent course, remaining localised to the lung for long periods before dissemination.
Thyroid MALT lymphoma
- Associated with: particularly associated with inflammatory conditions in the thyroid and salivary glands.
- Clinical features: thyroid mass, possible obstructive symptoms.
- Diagnosis: may need open biopsy.
- Treatment: surgery ± radiation for local disease; chemotherapy added if the disease is advanced.
Skin MALT lymphoma
- Associated with: B. burgdorferi infection may be associated but this is not clear.
- Clinical features: presents as a few, multiple, pink, red-to-violaceous papules, plaques, or nodules that most often involve the trunk or extremities, especially the arms.
- Treatment: options include observation only, excision, chemotherapy, radiotherapy.
- Prognosis: although recurrence is not uncommon, extracutaneous dissemination is very rare. Prognosis is excellent with five-year survival >95%.
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