Technically, extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT-lymphoma). Mucous membranes line many organs, and they contain lymphoid tissue, which is part of the lymphatic system.
The lymphatic system contains lymphocytes (white blood cells) that fight infections and cancer. In MALT lymphoma, one type of white blood cell, the B cell, in the mucosa-associated lymphoid tissue proliferates uncontrollably.
This form of non-Hodgkin’s lymphoma most often affects the stomach (gastric MALT lymphoma), but any mucosal membrane is susceptible: salivary glands, eye, lung, and skin. In general, MALT lymphoma affects slightly more women than men and occurs at an average age of 65 years.
Gastric MALT lymphoma most often develops from chronic Helicobacter pylori infection and the associated inflammation. Other bacterial infections are thought to be involved in the development of MALT lymphoma in other tissues. MALT lymphoma may also arise during the chronic inflammation caused by autoimmune diseases (especially Sjogren’s syndrome and Hashimoto’s thyroiditis).
Signs and Symptoms
The symptoms of MALT lumphoma are often specific to the organ involved:
- Gastric: dyspepsia (heartburn, nausea, and indigestion)
- Eye: sensitivity to light
- Lung: weight loss, fever, difficulty breathing, and cough
- Thyroid: signs mimic those of hypothyroidism (fatigue, muscle cramps, weight gain, and constipation)
- Skin: one or more patches of brown or red-brown lesions, largely on the extremities or back
- Breast: painless lump on the breast
- Salivary Glands: enlargement of the salivary glands and numbness somewhere in the face
Diagnosis and Staging
Diagnosis of all MALT lymphomas begins with a physical exam. Other tests are required, however, to make a definitive diagnosis. One of the most common tests for MALT lymphoma is a gallium scan.
This technique uses a radioactive form of gallium that acts like iron and accumulates in areas of inflammation (caused by, for example, infection) or rapid cell division (characteristic of cancer). Positron emission tomography (PET) is also used to image tumors.
Lymphomas in specific tissues are detected using approaches tailored to the site of the malignancy. Gastric MALT lymphoma is detected by removing a small sample of tissue during endoscopy, which is called esophagogastroduodenoscopy.
Doctors also test for the presence of H. pylori and use computed tomography (CT) to determine whether the cancer has spread. Chest X-rays can detect nodules of the less common lung MALT lymphoma, whereas a biopsy is often needed to diagnose a thyroid malignancy. Mammograms are typically used to detect lumps characteristic of a breast malignancy.
Lymphoma that affects the gastrointestinal tract (such as gastric MALT lymphoma) is classified into the following stages:
- Stage I: Tumor is confined to the gastrointestinal tract and may occur as a single tumor or multiple patches of cancerous cells; subdivided into stage I1 (small tumors limited to the mucosal layer ) and stage I2 (larger tumors that penetrate into submucosal layers)
- Stage II: tumor extends into the abdomen and has spread to lymph nodes; stage II1 tumors affect lymph nodes in the abdomen; stage II2 cancer has spread to more distant lymph nodes
- Stage IV: tumor has spread above the diaphragm or involves multiple extranodal sites
- Note: An “E” is used for stage II disease that has spread to organs adjacent to the gastrointestinal tract; the staging had been revised recently to eliminate stage III
The drug regimen used to eradicate H. pylori in gastric MALT lymphoma consists of two or three antibiotics in combination with a drug to reduce stomach acidity. Surgery is often reserved for persistent tumors or for those that have recurred.
Radiotherapy (either through an external beam or by a radioactive substance taken internally) is often used for bulky tumors that cannot be completely removed during surgery.
Chemotherapy is used for treatment-resistant lymphoma, or for malignancies that have spread to other parts of the body. Another drug used in treatment is rituximab, which is an antibody that destroys B cells by binding to a protein specifically expressed on the surface of these cells. Radiation, chemotherapy, or rituximab either alone or in combination are typically used for gastric MALT lymphomas that are not associated with H. pylori infection.
Radiotherapy and surgery are used for other types of MALT lymphoma. Chemotherapy is used if the cancer does not respond to these treatments or if the lymphoma has spread. Radiation is the treatment of choice for salivary gland MALT lymphoma, whereas both radiation and surgery have been used for breast involvement. Sometimes MALT lymphoma of the skin only requires close monitoring, but removal of the lesions or radiation are used if needed. Lung malignancies are treated surgically or with low-dose radiation and chemotherapy.
Up to 90% of gastric MALT lymphoma treatments are successful and about 70% of people with non-gastric MALT lymphoma survive for more than ten years. The probability of recurrence of any type of MALT lymphoma is about 40%. However, the chance of recurrent gastric MALT lymphoma is lower (approximately 22%).