What is MALT Lymphoma?

MALT Lymphoma: An Extranodal Marginal Zone B-Cell Lymphoma

What is MALT lymphoma?. Istockphoto.com/Stock Photo©Imtmphoto

What is MALT lymphoma, what are the causes, and how is it treated?

Overview

Lymphoma is a cancer of the kinds of white blood cells known as lymphocytes. MALT lymphoma is an uncommon form of non-Hodgkin lymphoma (NHL). MALT stands for "mucosa-associated lymphoid tissue." Unlike most lymphomas that begin growing within lymph nodes, this type of lymphoma typically arises from tissue that is present in the lining of certain other organs of the body.

There are different types of lymphocytes, and a person can develop lymphoma in any of these types. There are B-lymphocytes and T lymphocytes, for instance, and thus, there are B-cell lymphomas and T-cell lymphomas. MALT lymphoma is also known as an "extranodal marginal zone B-cell lymphoma," which conveys that it is a type of B-cell non-Hodgkin lymphoma that arises not from the lymph nodes but from other organs.

Prevalence

MALT lymphomas account for only about 5% of all non-Hodgkin lymphomas. They are more common in older adults but may occur in individuals in their twenties and thirties. They are slightly more common in women than in men.

Affected Organs

The most commonly affected organ in MALT lymphoma is the stomach, which accounts for nearly 2 out of every 3 cases. When a MALT lymphoma develops in the stomach, it may also be called a "gastric MALT lymphoma."  But other organs are also affected by MALT lymphoma.

The lung, thyroid, salivary glands and the eye may also be affected by this lymphoma.

Causes

MALT lymphomas of the stomach are associated with a bacterial infection. Helicobacter pylori is a type of bacteria that commonly infects the stomach and causes ulcers and gastritis, or irritation and inflammation of the stomach lining.

In some individuals, this bacterium can also cause MALT lymphomas. Gastric MALT lymphoma is not unique in this way in that other types of lymphoma have been linked to infections with certain bacteria, viruses, and parasites. This makes sense when you think of the lymph system, including its lymphocytes, as part of the immune system that works to identify and fight off foreign organisms in our body. Worldwide, roughly 20% of cancers are related to infections. Risk factors for MALT lymphomas also include infection with Chlamydophilia psittaci, and autoimmune diseases.

Behavior

MALT lymphomas are low-grade lymphomas. They grow slowly and remain confined to one organ for a relatively long time. When talking about lymphomas which are slow growing, oncologists often use the term 'indolent.' The majority of patients with MALT lymphoma are diagnosed early, before the disease has spread to other organs and lymph nodes.

Symptoms

The symptoms of MALT lymphoma depend on the organ that is affected. When MALT lymphoma affects the stomach, you may feel indigestion or you may experience weight loss; black stools are also possible because of bleeding into the stomach. Some people may feel a vague pain in the abdomen.

Diagnosis

To diagnose a MALT lymphoma, the doctor will need to take a biopsy from the tumor. For MALT lymphomas of the stomach, this usually involves an endoscopy. Doctors will also test for the presence of the H. pylori bacteria in the stomach. Other tests that will need to be performed include blood tests, scans of the abdomen and chest, and also a bone marrow test.

Staging

The staging of lymphomas involves 3 separate ratings. MALT lymphomas are first classified into different stages, ranging from stage I to stage IV based on how extensive they are. Then the letter A or B is given based on symptoms.

There are also 2 more letters, E and S, in which E stands for 'extra proliferative' or outside of the lymphatic system, and S represents the presence of cancer in the spleen.  MALT lymphomas do not arise in lymph nodes, nor do they commonly spread to other organs. Most MALT lymphomas are diagnosed in Stage IE, meaning they are present in only one organ and that it is outside of the lymphatic system.  Only about 20% of MALT lymphomas are in advanced stage at diagnosis.

Treatments

Treatment of MALT lymphomas depend on the organ involved and the stage of diagnosis. In most patients, local treatments like radiation or surgery may be adequate to deal with the disease, but systemic therapy such as chemotherapy is often used for higher stage cancers and may be used to reduce the risk of recurrence with early stage cancers.

Treatment of MALT lymphomas of the stomach consists of eradicating the infection with H pylori. This alone is sufficient to eliminate cancer in a large percentage of people. 

A Word From Verywell

The use of chemotherapy for MALT lymphomas has not been studied to the same extent as other lymphomas. In the past, it has been customary to use a type of chemotherapy that is used for low-grade non-Hodgkin lymphoma. In cases where antibiotic regimens fail, there is a good deal of consensus on the fact that chemotherapy should be used, but less agreement on the optimal therapeutic regimen.

Sources:

Nakamura, S., and T. Matsumoto. Treatment Strategy for Gastric Mucosa-Associated Lymphoid Tissue Lymphoma. Gastroenterology Clinics of North America. 2015. 44(3):649-60.

Raderer, M., Kiesewetter, B., Ferreri, A. et al. Clinicopathologic characteristics and treatment of marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), CA: A Cancer Journal for Clinicians. 2015 Nov 24. (Epub ahead of print).

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