MALT lymphoma overview

# Overview
MALT lymphoma is a common form of non-Hodgkin lymphoma (NHL) involving the mucosa-associated lymphoid tissue (MALT), frequently of the stomach, but virtually any mucosal site can be affected. It is a cancer originating from the B-cells in the marginal zone of the MALT. The evolution of gastric MALT lymphoma is a multistage process starting with the infection of H. pylori resulting in the recruitment of B- and T-cells and other inflammatory cells to the gastric mucosa. Genes involved in the pathogenesis of MALT lymphoma include FOXP1 and BCL6. A characteristic feature of MALT lymphoma is the presence of neoplastic cells within epithelial structures with associated destruction of the glandular architecture to form lymphoepithelial lesions. Most MALT lymphomas occur among individuals of 60 years of age. Males are more commonly affected with gastric MALT lymphoma than females. MALT lymphoma is usually slow growing (indolent), but some can be high grade. If left untreated, MALT lymphoma may progress to develop fever, anemia, weight loss, and large cell lymphoma. Complications of MALT lymphoma include anemia, cachexia, obstruction, and perforation of small intestine. The prognosis is good, and the 10-year survival rate for gastric MALT lymphoma is approximately 90% with a disease-free survival of approximately 70%. However, in rare instances, MALT lymphoma can progress and transform into aggressive high-grade tumors, such as extranodal diffuse large B cell lymphoma (eDLBCL), whereby the 10-year survival rate drops to approximately 42%. The staging of MALT lymphoma is based on two staging systems: Ann Arbor staging system and the TNM staging system. If the disease is limited to the stomach (which is assessed with computed tomography), then 70-80% of patients will have a complete regression on treatment with antibiotic eradication of H. pylori. The optimal therapy for MALT lymphoma depends on the stage at diagnosis. The treatment options for early stage (localized) gastric MALT lymphoma include antibiotic therapy, radiotherapy, chemotherapy, surgery, and monoclonal antibodies. The treatment options for advanced stage gastric MALT lymphoma include observation, radiotherapy, chemotherapy, and monoclonal antibodies. Secondary prevention strategies following MALT lymphoma include urease breath test, performed 4-6 weeks after completion of the course of antibiotic therapy, and endoscopy with concurrent biopsy, performed 3-6 months after the treatment is finished.

# Historical Perspective
MALT lymphoma was first described by Isaacson and Wright in 1983.

# Classification
There is no classification system established for MALT lymphoma.

# Pathophysiology
MALT lymphoma is a form of lymphoma involving the mucosa-associated lymphoid tissue (MALT), frequently of the stomach, but virtually any mucosal site can be afflicted. It is a cancer originating from B cells in the marginal zone of the MALT. The evolution of gastric MALT lymphoma is a multistage process starting with the infection of H. pylori resulting in the recruitment of B- and T-cells and other inflammatory cells to the gastric mucosa. Genes involved in the pathogenesis of MALT lymphoma include FOXP1 and BCL6. Chromosomal translocations are also involved in the pathogenesis of MALT lymphoma, which include t(1;14)(p22;q32), t(11;18)(q21;q21), t(14;18)(q32;q21), and t(3;14)(p14.1;q32). Gastric MALT lymphoma is frequently associated with chronic inflammation as a result of the presence of Helicobacter pylori (72-98%). On microscopic histopathological analysis, MALT lymphoma is characterized by the presence of dense diffuse lymphoid infiltrate of marginalzone cells in lamina propria with prominent lymphoepithelial lesions and consisting of small atypical cells with monocytoid features. A characteristic feature of MALT lymphoma is the presence of neoplastic cells within epithelial structures with associated destruction of the glandular architecture to form lymphoepithelial lesions. The neoplastic cells of MALT lymphoma may be positive for B-cell associated antigens (CD19, CD20, CD22, CD79a) that co-express BCL-2, and are negative for CD5, CD10, CD43, and cyclin D1.

# Causes
Common causes of gastric MALT lymphoma include H.pyroli infection, long-term immunosuppressant drug therapy, and HIV infection. Common causes of non gastric MALT lymphoma include autoimmune disorders, such as Hashimoto's thyroiditis and Sjogrens syndrome.

# Differentiating MALT Lymphoma from other Diseases
MALT lymphoma must be differentiated from gastric carcinoma, gastritis, diffuse large B cell  lymphoma, follicular lymphoma, small cell lymphocytic lymphoma, and mantle cell lymphoma.

# Epidemiology and Demographics
MALT lymphoma is the third most common type and accounts for approximately 8% of all cases of non-Hodgkin lymphoma. MALT lymphoma is a disease that tends to affect the elderly population. Most MALT lymphomas occur in people in their 60's. Males are more commonly affected with gastric MALT lymphoma than females. The male to female ratio is approximately 2.43 to 1. There is no racial predilection to MALT lymphoma.

# Risk Factors
The most potent risk factor in the development of gastric MALT lymphoma is H.pylori infection. Approximately 510% of people with gastric MALT lymphoma, however, do not have an H. pylori infection (H. pylori negative). Other risk factors for gastric MALT lymphoma include long-term immunosuppressant drug therapy and HIV infection. Common risk factors in the development of MALT lymphoma, in areas of the body other than the stomach, are autoimmune disorders such as Hashimoto's thyroiditis, Sjogrens syndrome, and Celiac disease.

# Screening
There is insufficient evidence to recommend routine screening for MALT lymphoma.

# Natural History, Complications and Prognosis
MALT lymphoma is usually slow growing (indolent), but some can be high grade. If left untreated, MALT lymphoma may progress to develop fever, anemia, weight loss, and large cell lymphoma. Complications of MALT lymphoma include anemia, cachexia, obstruction, and perforation of small intestine. The prognosis is good, and the 10-year survival rate for gastric MALT lymphoma is approximately 90% with a disease-free survival of approximately 70%. However, in rare instances, MALT lymphoma can progress and transform into aggressive high-grade tumors, such as extranodal diffuse large B cell lymphoma (eDLBCL), whereby the 10-year survival rate drops to approximately 42%.

# Diagnosis

## Staging
The staging of MALT lymphoma is based on two staging systems: Ann Arbor staging system and the TNM staging system.

## History and Symptoms
When evaluating a patient for MALT lymphoma, detailed history of the presenting symptom (onset, duration, and progression), other associated symptoms, and a thorough family and past medical history should be reviewed. Other specific areas of focus when obtaining the history include the review of common associated conditions such as H. pylori associated gastritis and autoimmune disorders, such as Hashimoto's thyroiditis, Sjogrens syndrome, and Celiac disease. Symptoms of MALT lymphoma depend on the location of the tumor: gastric and non gastric. Symptoms of MALT lymphoma include epigastric pain, fatigue, heartburn, fever, cough with blood in sputum, shortness of breath, and/or lump in the superior lateral quadrant of the orbit, breast, neck, or salivary gland.

## Physical Examination
Physical examination findings of MALT lymphoma depend on the location of the tumor: Gastric and non gastric. The majority of patients with MALT lymphoma often have no physical findings and lymphadenopathy is uncommon.

## Laboratory Findings
Complete blood count is performed to check the blood counts. Liver function tests and renal function tests are performed to assess the liver and kidneys, respectively.

## Upper GI Endoscopy
The gastric lesion of MALT lymphoma on upper GI endoscopy may look inflamed or ulcerated. Occasionally, a nodular mass, similar to a reactive lymph node, may be visualized.

## CT
Chest, abdominal, and/or pelvic CT scan is generally performed to evaluate the extent and spread of MALT lymphoma. If the disease is limited to the stomach (which is assessed with computed tomography), then 70-80% of patients will have a complete regression on treatment with antibiotic eradication of H. pylori.

## MRI
Chest, abdominal, and/or pelvic CT scan is generally performed to evaluate the extent and spread of MALT lymphoma.

## Endoscopic Ultrasound
Endoscopic ultrasound may be performed to detect the extent of spread of MALT lymphoma through the stomach wall. The endoscopic ultrasound scan may demonstrate the deeper tissues that lie to the stomach lining and also involvement of any adjacent lymph nodes.

## Biopsy
Organ specific endoscopic tissue biopsy is diagnostic of MALT lymphoma. To view findings on biopsy characteristic of MALT lymphoma, click here.

## Other Imaging Findings
Other imaging studies for MALT lymphoma include barium studies and PET scan. Barium contrast studies of the esophagus, stomach, small intestine, or the colon may be performed to demonstrate any filling defect in the barium flow which denotes to the presence of any infiltrative mass due to MALT lymphoma. FDG-PET scan may be helpful in diagnosis, staging, and follow-up of MALT lymphoma.

## Other Diagnostic Studies
There are no other diagnostic studies associated with MALT lymphoma.

# Treatment

## Medical Therapy
The optimal therapy for MALT lymphoma depends on the stage at diagnosis. The treatment options for early stage (localized) gastric MALT lymphoma include antibiotic therapy, radiotherapy, chemotherapy, surgery, and monoclonal antibodies. The treatment options for advanced stage gastric MALT lymphoma include observation, radiotherapy, chemotherapy, and monoclonal antibodies.

## Surgery
Surgery is not the first-line treatment option for patients with gastric MALT lymphoma. Partial or total gastrectomy is usually reserved for patients with early stage gastric MALT lymphoma, if the lymphoma remains after antibiotic therapy or if the gastric lymphoma progresses.

## Primary Prevention
There are no primary preventive measures available for MALT lymphoma.

## Secondary Prevention
Secondary prevention strategies following MALT lymphoma include urease breath test, performed 4-6 weeks after completion of the course of antibiotic therapy, and endoscopy with concurrent biopsy, performed 3-6 months after the treatment is finished.