Marginal Zone Lymphoma (MZL)

Mucosa-associated lymphoid tissue (MALT) lymphoma is the most common type of MZL. This MZL subtype is also called “extranodal” MZL because it doesn’t start in lymph nodes. Instead, it forms in other lymphatic tissue found throughout the body. When a MALT lymphoma develops in the stomach it is referred to as a gastric MALT lymphoma. However, MALT lymphomas can also form in other parts of the body (non-gastric MALT), including the skin, thyroid, lungs, bowels, salivary glands or around the eye. MALT lymphoma is usually slow-growing and responds well to treatment.

Splenic marginal zone B-cell lymphoma (SMZL) is a rare type of MZL that usually arises in the spleen. Similar to MALT lymphoma, SMZL tends to grow and spread slowly, and treatment may be safely delayed until symptoms arise.

Nodal marginal zone lymphoma (NMZL) is even rarer than SMZL and develops in lymph nodes. This slow-growing type of MZL rarely spreads beyond lymph nodes.

MZL usually affects older patients, with the majority of cases in people above 60 years of age. Furthermore, MZL is slightly more common in men than in women. The latter is not the case for NMZL which is slightly more common in women. In many patients, the cause of the MZL is unclear. However, researchers did find out that certain bacterial infections (e.g., Heliobacter pylori) increase the risk for gastric-MALT lymphoma, whereas a chronic hepatitis C infection increases the risk for SMZL or NMZL. In addition, certain autoimmune disorders (e.g., lupus, rheumatoid arthritis) increase the risk for non-gastric MALT.

The diagnostic process for MZL starts with a physical examination, during which the doctor palpates lymph nodes and other areas of the body to check for swelling. The doctor will also assess the medical history of the patient to better understand the general health status and any potential risk factors. If a lymphoma is suspected, a biopsy of an affected area (e.g., lymph node, spleen) is performed to make a final diagnosis. This tissue sample is sent to a laboratory, where a pathologist assesses whether the specimen contains cancerous cells and performs additional tests to determine the exact nature of the cancer cells.

If this analysis is indicative for MZL, additional tests can be performed to assess how far the cancer has spread. This includes imaging tests (e.g., PET-CT, MRI) to look for signs of MZL in other areas of body and a blood test to check for viral and bacterial infections.

The treatment selection for patients with MZL depends on the type, stage, and location of the disease, the patient’s age, the overall health status, and whether or not the patient presents with lymphoma-related signs or symptoms.

Since gastric MALT lymphoma is often the result of a bacterial infection, the initial treatment usually consists of antibiotics. If the gastric-MALT lymphoma relapses (disease returns after treatment) or does not respond to this treatment (i.e., refractory disease), the available treatment options include radiation therapy for patients with localized disease or a systemic treatment with the monoclonal antibody rituximab, alone or in combination with chemotherapy, for patients with more advanced disease.

For patients with nodal MZL, or non-gastric MALT lymphoma, active treatment is usually deferred to the time when symptoms develop. In patients with localized disease, this treatment typically consists of radiation therapy. For patients with more advanced MZL the treatment includes immunotherapy with the monoclonal antibody rituximab, either alone, or in combination with chemotherapy.

In patients with SMZL, a splenectomy is often curative. Finally, given the association of this type of MZL with hepatitis C, treating the hepatitis C infection may also cure the lymphoma.