MALT Lymphoma, also known as extranodal marginal zone B-cell lymphoma, is a slow-growing type of non-Hodgkin lymphoma. The acronym MALT stands for Mucosa-Associated Lymphoid Tissue, referring to specialized immune tissue found in the moist linings of various organs and body cavities. These include areas like the stomach, lungs, salivary glands, thyroid, and eyes.
This lymphoma originates from B lymphocytes, a type of white blood cell. Unlike some other lymphomas, MALT lymphoma develops outside traditional lymph nodes, in these mucosal tissues. It is considered an indolent cancer and often remains localized in its early stages.
Associated Conditions and Causes
MALT lymphoma often develops in body areas with long-term inflammation, frequently due to chronic infections or autoimmune conditions. A link exists between chronic Helicobacter pylori (H. pylori) infection and gastric MALT lymphoma. This bacterium infects the stomach lining, causing persistent inflammation that can lead to lymphoma formation. While H. pylori infection is widespread, only a small percentage of infected individuals develop gastric MALT lymphoma.
Other chronic infections and autoimmune diseases are associated with non-gastric MALT lymphomas. For instance, MALT lymphoma affecting the salivary glands is linked to Sjögren’s syndrome, an autoimmune disorder causing dry eyes and mouth. Hashimoto’s thyroiditis, an autoimmune condition affecting the thyroid gland, can be associated with MALT lymphoma in that organ. Other bacterial infections, such as Borrelia burgdorferi (linked to skin MALT lymphoma) and Chlamydophila psittaci (linked to ocular MALT lymphoma), have also been implicated.
Common Locations and Corresponding Symptoms
The symptoms of MALT lymphoma vary widely depending on where it develops in the body. Since it arises in mucosal tissues, signs often relate directly to the function or presence of a mass in the affected organ.
Stomach (Gastric MALT Lymphoma)
Gastric MALT lymphoma is the most common form, often presenting with symptoms related to digestive upset. Individuals may experience persistent indigestion, upper abdominal pain, nausea, or vomiting. Less commonly, it can lead to gastrointestinal bleeding, manifesting as dark stools or blood in vomit, or unexplained weight loss.
Lungs
When MALT lymphoma affects the lungs, symptoms can resemble common respiratory conditions. Patients might develop a persistent cough or experience shortness of breath. Chest pain or coughing up blood could also occur.
Eyes (Ocular Adnexa)
MALT lymphoma in the ocular adnexa, which includes tear ducts and tissues around the eye, can cause visible changes and affect vision. Symptoms may include redness, swelling around the eye, or a noticeable mass. Drooping eyelids or blurry vision can also be present.
Salivary Glands
If the salivary glands are involved, typically those in front of the ears or under the chin, a noticeable swelling or lump in the jaw area may be the primary symptom. This swelling can sometimes cause discomfort, though it is often painless.
Thyroid
MALT lymphoma in the thyroid gland often presents as a lump in the neck. This lump may be felt by the individual or discovered during a medical examination. Difficulty swallowing can also occur if the mass is large enough to press on the esophagus.
The Diagnostic Process
Confirming a diagnosis of MALT lymphoma involves a series of tests, with a biopsy being the definitive step. A biopsy involves taking a small tissue sample from the suspicious area, which is then examined under a microscope by a pathologist. The method of obtaining the biopsy depends on the lymphoma’s location; for instance, an endoscopy is commonly used for gastric MALT lymphoma, allowing direct visualization and sampling of the stomach lining. For other sites, a needle biopsy or surgical excision might be performed.
Once lymphoma cells are identified, further tests determine the extent of the disease, known as staging. Imaging techniques such as computed tomography (CT) scans and positron emission tomography (PET) scans help visualize the lymphoma’s spread. Blood tests are also part of the diagnostic workup, including a complete blood count, lactate dehydrogenase (LDH) levels, and tests for associated infections like H. pylori or Hepatitis C. These evaluations guide treatment decisions.
Standard Treatment Protocols
Treatment for MALT lymphoma is individualized, considering its location, cause, and spread. For gastric MALT lymphoma linked to H. pylori infection, initial treatment involves antibiotics. This eradication therapy typically lasts 7 to 14 days and aims to clear the bacterial infection, which can lead to lymphoma remission in many cases (50-95%). Follow-up tests, such as a breath test or stool sample, are usually performed several weeks after antibiotic treatment to confirm H. pylori eradication.
If the lymphoma does not respond to antibiotic therapy, or if it is a non-gastric MALT lymphoma not associated with an infection, localized radiation therapy is a common approach. Radiation effectively targets and destroys lymphoma cells in a specific area, especially for early-stage disease. For more widespread MALT lymphoma, or when other treatments have not been successful, systemic therapies may be considered. These can include immunotherapy, often with drugs like rituximab, which targets specific proteins on lymphoma cells, or chemotherapy, which uses drugs to kill cancer cells throughout the body. Some slow-growing, non-symptomatic cases may also be managed with watchful waiting, where the lymphoma is closely monitored without immediate intervention.