Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, or MALT lymphoma, is a slow-growing type of non-Hodgkin lymphoma that develops in the lymphoid tissue outside the lymph nodes.
MALT lymphoma is the most common form of marginal zone lymphoma, though it’s still rare. It’s estimated that about 5,000 new cases of MALT lymphoma are diagnosed in the U.S. each year, according to lymphoma specialist Dai Chihara, M.D., Ph.D.
The stomach is the most common site for MALT lymphoma. This is known as gastric MALT lymphoma. It can also be found in other parts of the gastrointestinal tract.
“It’s important to note that this is not a primary stomach cancer,” says Gunther. “This is lymphoma that occurs in the stomach.”
Non-gastric MALT lymphoma most commonly affects the lungs, salivary glands, tissues around the eye and skin.
What are the symptoms of MALT lymphoma?
Symptoms can vary, depending on where the lymphoma is in the body. Some people may not have any symptoms, and the cancer is found incidentally when a doctor is testing for something else.
For gastric MALT lymphoma, symptoms often mimic those of an upset stomach and can include:
Non-gastric MALT lymphoma may cause the following symptoms, depending on where it occurs in the body:
salivary gland: a mass you can feel or that shows up in imaging
lung: cough or shortness of breath
skin: a small bump on the skin that can resemble a bug bite or pimple
“If you have any of these symptoms for longer than a couple of weeks without improvement, or if the symptoms are worsening, you should see a doctor to be evaluated,” says Gunther.
What causes MALT lymphoma?
Some MALT lymphomas are associated with autoimmune disorders and infections, depending on where the lymphoma is located.
Helicobacter pylori (H. Pylori) infection, a common bacterial infection that can cause stomach ulcers, increases the risk for gastric MALT lymphoma. Many gastric MALT lymphoma patients will have an H. Pylori infection.
“The H. Pylori infection causes chronic inflammation in the stomach, which is thought to increase the risk of gastric MALT lymphoma,” says Chihara.
MALT lymphoma on the skin may be linked to Borrelia burgdorferi infection, while the autoimmune disorder Sjogren’s syndrome can increase the risk of MALT lymphoma in the salivary glands.
How is MALT lymphoma diagnosed?
Doctors need biopsies to diagnose MALT lymphoma. The type of biopsy depends on where the lymphoma has developed.
An interventional radiology image-guided biopsy may be used to diagnose MALT lymphoma in the salivary glands or lungs. A bronchoscopy can also be used for the lungs.
An endoscopy may be used to diagnose gastric MALT lymphoma.
After a MALT lymphoma diagnosis is made, doctors will try to determine the cancer stage.
“With MALT lymphoma, it’s more common for patients to be diagnosed with early-stage disease, or localized disease that hasn’t spread to distant lymph nodes or other parts of the body,” says Gunther.
Patients with gastric MALT lymphoma can be given antibiotics first to treat H. Pylori. Treating the infection often clears away the lymphoma.
If antibiotics don’t work, patients with early-stage MALT lymphoma receive radiation therapy.
If MALT lymphoma is not localized, and if you’re not experiencing any problems from the cancer, your doctor may choose to monitor you closely, rather than prescribing treatment.
“MALT lymphoma is often a very slow-growing disease, and people can live with it for long periods, sometimes without even knowing they have it,” says Gunther. “MALT lymphoma is treatable in most cases. We don’t want to cause the patient more harm with the treatment than the disease itself.”
For patients with progressive advanced-stage MALT lymphoma that is causing symptoms or trouble, there are systemic treatment options.
The first systemic treatment option is the monoclonal antibody rituximab or chemoimmunotherapy, which is a combination of chemotherapy and immunotherapy. You may be given a chemotherapy drug, such as CHOP or bendamustine plus rituximab.
Recurrent MALT lymphoma may be treated with oral drugs, such as BTK inhibitors ibrutinib and zanubrutinib, or the immunotherapy drug lenalidomide.
What new research is being done to advance MALT lymphoma treatment?
Gunther recently led a clinical trial looking at reducing the radiation dosage for gastric MALT lymphoma patients.
“In the past, the standard dose for radiation was at least two-and-a-half weeks of treatment. But because of the positive response to low-dose radiation in this type of cancer, we’ve been looking to reduce the dose,” explains Gunther.
In the clinical trial, patients started with ultra-low-dose radiation, or just two days of treatment.
“We gave additional treatment — another 10 days of radiation — only to those patients who did not experience a complete response after the initial two days,” she says. “This spared a majority of patients unnecessary treatment and side effects.”
Because MALT lymphoma is rare, more research is needed to help determine which treatments work best for patients with MALT lymphoma. But Chihara notes that MD Anderson continues to pursue new clinical trials with the goal of expanding treatment options for patients with MALT lymphoma.