Mucosa-Associated Lymphoid Tissue (MALT) lymphoma is a type of cancer that originates in the body’s immune tissue. This condition is a form of non-Hodgkin lymphoma, meaning it develops from lymphocytes, a type of white blood cell involved in the immune system.
What is MALT Lymphoma?
MALT lymphoma is classified as an extranodal marginal zone B-cell lymphoma, meaning it starts in B-cells outside of the lymph nodes. This type of lymphoma is considered slow-growing (indolent). It arises in mucosal sites, often developing in response to chronic inflammation or autoimmune processes.
MALT, or Mucosa-Associated Lymphoid Tissue, is a component of the immune system found in the moist lining of various organs and body cavities (mucous membranes). These areas include the gastrointestinal tract, lungs, and skin. While MALT lymphoma can occur in various locations, it most commonly develops in the stomach, accounting for 35% to 50% of cases. Other common sites include the salivary glands, thyroid gland, lungs, skin, and tissues around the eye.
What Causes MALT Lymphoma?
MALT lymphoma development is associated with chronic inflammation, especially gastric MALT lymphoma. The bacterium Helicobacter pylori is a primary cause for gastric MALT lymphoma, linked to approximately 90% of cases. H. pylori causes chronic inflammation in the stomach lining, leading to continuous stimulation of immune cells, which can eventually result in the malignant transformation of B-lymphocytes.
Beyond H. pylori, other chronic inflammatory or autoimmune diseases connect to non-gastric MALT lymphomas. For instance, Sjögren’s syndrome, an autoimmune disorder, is associated with MALT lymphoma in the salivary glands. Hashimoto’s thyroiditis, another autoimmune condition, is linked to MALT lymphoma of the thyroid gland. MALT lymphoma is not considered contagious, nor is it inherited.
Recognizing and Diagnosing MALT Lymphoma
Symptoms of MALT lymphoma are general and vary depending on the affected organ. For instance, gastric MALT lymphoma might present with indigestion, abdominal pain, heartburn, or acid reflux. These symptoms are also common in less serious stomach conditions. If the lymphoma is in the salivary glands, a noticeable mass or swelling might be present. Ocular MALT lymphoma can lead to symptoms like drooping eyelids, irritated eyes, swelling around the eyes, or double vision.
The diagnostic process begins with a medical evaluation based on reported symptoms. Imaging studies identify the location and extent of potential lesions; for gastric MALT lymphoma, an endoscopy visualizes the stomach lining, while for other sites, computed tomography (CT) scans, magnetic resonance imaging (MRI), or positron emission tomography (PET) scans assess the disease’s spread.
A biopsy, taking a tissue sample for pathological examination, is necessary to confirm the diagnosis. Specialized tests, such as immunohistochemistry and genetic analysis, are performed on the biopsy sample to characterize the lymphoma cells. Staging tests, including bone marrow biopsies and PET scans, determine disease spread.
Treating MALT Lymphoma
Treatment strategies for MALT lymphoma are tailored based on the lymphoma’s location, its stage, and whether a Helicobacter pylori infection is present. For gastric MALT lymphoma associated with H. pylori, antibiotic eradication therapy is the effective first-line treatment. This involves a 7 to 14-day course of antibiotics combined with acid-reducing medication, leading to complete remission in a significant number of patients, sometimes up to 75%.
If the gastric MALT lymphoma is not linked to H. pylori, or if it does not respond to antibiotic treatment, other approaches are considered. For localized disease, radiation therapy is an effective option, with response rates exceeding 90%. In some cases, especially for early-stage disease without significant symptoms, a “watch and wait” approach (active surveillance) may be adopted. For more widespread or aggressive cases, systemic treatments like chemotherapy or immunotherapy, such as rituximab, may be used. MALT lymphoma has a favorable prognosis, especially when localized and responsive to initial treatments.