Extranodal Marginal Zone B-cell Lymphoma (MALT Type)
Extranodal marginal zone B-cell lymphoma, commonly called MALT lymphoma, is a rare, slow-growing cancer that develops in the moist tissues lining organs and body cavities, most often in the stomach, lungs, or tissues around the eyes.
Table of contents
- What is MALT lymphoma?
- Other names for this condition
- Parts of the body affected
- Who develops MALT lymphoma?
- What causes MALT lymphoma?
- Signs and symptoms
- How is MALT lymphoma diagnosed?
- Treatment options
- What to expect
What is MALT lymphoma?
Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (called MALT lymphoma) is a type of slow-growing cancer that affects the lymphatic system, which is part of the body’s defense system against germs[1]. The lymphatic system includes organs, glands, tubes, and clusters of cells called lymph nodes that work together to fight infections[3].
MALT lymphoma is classified as a non-Hodgkin lymphoma, which means it is one type among many different lymphomas[3]. It belongs to a group called marginal zone lymphomas because it develops from B cells (a type of white blood cell) located in an area at the edge of lymphoid tissue called the marginal zone[8].
This condition develops in the mucosa, which is the moist tissue that lines organs and body cavities, including the nose, mouth, lungs, and digestive system[8]. The word “extranodal” means that the cancer starts in body organs rather than in lymph nodes[4]. MALT lymphoma accounts for about 7 to 8 percent of all B-cell lymphomas[1].
Most people are diagnosed when the disease is at an early stage and limited to one area of the body[1]. The outlook is generally good, even when the lymphoma has spread to multiple areas[8]. However, in 25 to 50 percent of cases, the disease may be found in more than one location at the time of diagnosis[1].
MALT lymphoma, extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, extranodal MZL
Other names for this condition
Healthcare providers may use several different names when referring to this condition. It is most commonly called MALT lymphoma. Other names include extranodal marginal zone lymphoma, extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, and extranodal MZL[4][8].
Parts of the body affected
- Stomach (most common site)
- Lungs
- Ocular adnexa (tissues around the eye)
- Salivary glands
- Thyroid gland
- Skin
- Breasts
- Intestines
- Bladder
MALT lymphoma can develop in various organs throughout the body. The stomach is the most common location, accounting for more than 30 percent of cases[14]. When it affects the stomach, doctors call it gastric MALT lymphoma[4].
Other frequent sites include the lungs, the tissues around the eye (called ocular adnexa), salivary glands, thyroid gland, and skin[7]. Less commonly, it can affect the intestines, breasts, bladder, and other organs[4]. When MALT lymphoma develops in organs other than the stomach, healthcare providers call it non-gastric MALT lymphoma[8].
In some cases, the disease can involve multiple extranodal sites, particularly in paired organs such as both salivary glands or different parts of the digestive tract[7]. The bone marrow may also be affected, though this is less common in gastric cases and more frequent when the lymphoma arises in the lung or tissues around the eyes[7].
Who develops MALT lymphoma?
MALT lymphoma typically affects older adults, with a median age at diagnosis of about 60 years[1]. Some sources indicate that people age 65 and older are most commonly affected[25]. The condition tends to be more common in men than in women[5][25].
People who have a family history of lymphoma are at higher risk of developing MALT lymphoma[5][12]. Additionally, having certain infections or autoimmune diseases (conditions where the body’s defense system attacks its own tissues) can increase the likelihood of developing this condition[5][8].
What causes MALT lymphoma?
Several factors can drive the development of MALT lymphoma. In many cases, the condition is linked to long-lasting inflammation caused by infectious agents or autoimmune disorders[9].
The strongest connection is between gastric MALT lymphoma and a bacterial infection called Helicobacter pylori (H. pylori), which causes chronic inflammation of the stomach lining[3]. Many people with gastric MALT lymphoma have a history of this infection[4]. The bacteria stimulate the immune system continuously, which over time can lead to the development of lymphoma[1].
Other infections have been associated with MALT lymphoma in different body sites. These include Chlamydophila psittaci in the tissues around the eye, Borrelia burgdorferi in the skin, Achromobacter xylosoxidans in the lungs, and hepatitis C virus in various locations[14][4].
Autoimmune diseases also play a role in some cases. MALT lymphoma of the salivary gland is often linked to an autoimmune condition called Sjögren’s syndrome, while MALT lymphoma of the thyroid can be connected to Hashimoto’s thyroiditis, another autoimmune disorder[8][5].
The continuous stimulation of immune cells through these infections and inflammatory conditions can eventually cause changes in B cells that turn them into cancer cells[1][14].
Signs and symptoms
MALT lymphoma grows very slowly, and in many cases, people may not have any symptoms at all[5][8]. Some individuals receive a diagnosis while undergoing tests for unrelated health issues[25].
When symptoms do occur, they vary depending on where in the body the lymphoma has developed. Because MALT lymphoma usually develops outside the lymph nodes, it typically does not cause swollen lymph nodes[8].
When MALT lymphoma affects the stomach (gastric MALT), common symptoms include indigestion or heartburn, belly pain, nausea and vomiting, feeling full even when you have not eaten much, unexplained weight loss, and sometimes bleeding in the digestive tract[5][8].
Non-gastric MALT lymphoma produces different symptoms depending on its location. When it affects tissues around the eyes, it may cause drooping eyelids, irritated or reddened eyes, swelling around the eyes, or double vision[5]. In the lungs, it can lead to shortness of breath, chest pain, or coughing, sometimes with blood[5][8].
If the lymphoma develops in the salivary glands, you might notice swelling in the glands located in front of your ears, under your chin, or inside your mouth[5]. When it affects the skin, it may appear as red, pink, or purple patches or lumps[5].
MALT lymphoma of the thyroid gland may produce symptoms of an underactive thyroid, such as fatigue, dry skin, unexplained weight gain, or increased sensitivity to cold. You might also notice a lump at the front of your neck[5].
Some people experience general symptoms such as fever, night sweats, and unexplained weight loss[5].
How is MALT lymphoma diagnosed?
To diagnose MALT lymphoma, healthcare providers begin by asking about your symptoms, your medical history, and your family medical history[5]. They want to know if you have had certain infections or autoimmune conditions that might increase your risk.
The main test used to diagnose MALT lymphoma is a biopsy, which involves removing a small sample of tissue from the affected area[8]. A specialist then examines this sample under a microscope to look for cancer cells. How the biopsy is performed depends on where the suspected lymphoma is located.
For gastric MALT lymphoma, doctors perform a gastroscopy (also called an endoscopy). During this procedure, a thin tube with a camera is passed through your mouth into your stomach so the doctor can look at the stomach lining and take tissue samples from any abnormal-looking areas[8].
For MALT lymphoma in other parts of the body, different procedures may be used. A bronchoscopy can take a biopsy from the lungs, while a colonoscopy can sample tissue from the bowel[8].
Blood tests are usually performed as part of the diagnostic process. For gastric MALT lymphoma, doctors test for H. pylori infection[8]. Other blood tests may include a complete blood count (CBC), tests for liver and kidney function, and measurements of certain substances that can indicate the presence of cancer[5].
Once MALT lymphoma is confirmed, additional tests help determine how far the disease has spread. These may include imaging tests such as computed tomography (CT scans), examination of bone marrow, and endoscopic investigations if needed[1].
Treatment options
Treatment for MALT lymphoma depends on several factors, including where the lymphoma is located, how far it has spread, whether you have symptoms, and your overall health[4][11].
Treatment for gastric MALT lymphoma
Because gastric MALT lymphoma is often caused by H. pylori infection, the initial treatment usually involves antibiotics to eliminate the bacteria[4]. Doctors typically prescribe antibiotics along with drugs called proton pump inhibitors (PPIs), which reduce stomach acid production. This treatment is usually given for two weeks[11].
In about 90 percent of cases, the lymphoma goes away completely after antibiotic and PPI treatment, although this may take several months[11]. Treating the H. pylori infection and hepatitis C virus (if present) can often clear the lymphoma completely, and you may not need any additional treatment[4].
If the lymphoma returns after antibiotic therapy or does not respond to treatment, other options are available. These include rituximab (a targeted therapy drug), radiation therapy, and in some cases, surgery[11].
Treatment for non-gastric MALT lymphoma
Treatment for non-gastric MALT lymphoma varies based on where the lymphoma is located and how far it has spread. In some cases, if the lymphoma is growing slowly and not causing symptoms, your healthcare team may recommend watchful waiting (also called active surveillance)[4][11]. With this approach, your health and disease are monitored through regular checkup visits and tests. Treatment starts if you begin to develop symptoms or if tests show the disease is progressing[4].
Radiation therapy uses high-energy rays to destroy cancer cells. It may be used to treat MALT lymphoma that is located in specific areas of the body, such as the stomach or lungs[4]. Studies have shown that radiation therapy alone can be highly effective for localized MALT lymphoma, particularly in the tissues around the eyes, with excellent survival rates and few serious complications[6][13].
For certain locations like the lung or breast, surgery may be part of the treatment plan[11].
Targeted therapy uses drugs that target specific molecules on or inside cancer cells. Rituximab is a targeted therapy drug commonly used to treat MALT lymphoma. It can be used alone or combined with chemotherapy[4].
Chemotherapy uses drugs to destroy cancer cells. You may be offered chemotherapy for MALT lymphoma, often combined with rituximab[4]. Common chemotherapy regimens include bendamustine plus rituximab and R-CHOP (rituximab combined with several chemotherapy drugs)[11].
For MALT lymphoma affecting the area around the eyes (ocular adnexal lymphoma), antibiotic therapy such as doxycycline has shown effectiveness, particularly when the condition is associated with infection[11].
More advanced disease that has spread to multiple areas is usually treated with a combination of immunotherapy and chemotherapy[11].
What to expect
MALT lymphoma is typically a slow-growing cancer with a generally favorable outlook[1][8]. Most people present with early-stage disease that is limited to one or two areas of the body, and the prognosis is good even when the lymphoma is more widespread[8].
For localized MALT lymphoma treated with appropriate therapy, outcomes are excellent. Studies of MALT lymphoma in the tissues around the eyes showed 3-year overall survival and event-free survival rates of 100 percent and 97 percent, respectively[6][13].
The condition has an indolent (slow-growing) behavior, meaning it typically develops slowly over time[1]. Treatment can often put the disease into remission, though in some cases the lymphoma may return and require additional treatment[25].
In rare cases, MALT lymphoma can transform into a more aggressive type of lymphoma called diffuse large B-cell lymphoma (DLBCL). When this happens, the disease is treated as DLBCL[4][10].
Your healthcare team will continue to monitor you after treatment through regular follow-up visits and tests to check for any signs that the lymphoma has returned or is progressing.
