MALT lymphoma

Mucosa-associated lymphoid tissue (MALT) lymphoma is categorized as indolent or low-grade B-cell lymphoma; however, high-grade histologic transformation can occur.

Median age at presentation is 61 years.

The stomach is the most frequently involved organ, and in most cases (90%), there is a strong association between gastric MALT lymphoma and chronic Helicobacter pylori infection.

Other sites that may be involved include the salivary glands, eyes, lung, intestinal tract, skin, and thyroid gland. May also occur (rarely) in breasts, dura, and genitourinary tract. Autoimmune diseases have been linked to nongastric MALT lymphoma.

Diagnosis is based on history, physical exam, radiologic imaging studies, histopathologic and immunohistochemical evaluation of the biopsy specimen, and molecular laboratory techniques.

Treatment is based on the histologic subtype and severity of symptoms at presentation. Surgery, radiation therapy, and chemotherapy all play a role. H pylori-eradication therapy is the mainstay of treatment for localized H pylori-positive gastric MALT lymphoma.

The World Health Organization (WHO) has defined mucosa-associated lymphoid tissue (MALT) lymphoma as "an extranodal lymphoma composed of morphologically heterogenous small B cells, including marginal zone cells, cells resembling monocytoid cells, small lymphocytes, and scattered immunoblasts and centroblast-like cells".[1]Jaffe ES, Harris NL, Stein H, et al, eds. World Health Organization classification of tumors. Pathology and genetics: tumors of haemopoietic and lymphoid tissues. Lyon, France: IARC Press; 2008. Plasma cell differentiation occurs in a proportion of cases. The infiltrate is located in the marginal zone of reactive B-cell follicles and extends into the interfollicular region. Lymphoepithelial lesions develop in epithelial tissues due to infiltration of the epithelium with neoplastic cells.[1]Jaffe ES, Harris NL, Stein H, et al, eds. World Health Organization classification of tumors. Pathology and genetics: tumors of haemopoietic and lymphoid tissues. Lyon, France: IARC Press; 2008. The stomach is the most commonly involved organ, and there is an important association with chronic Helicobacter pylori infection in the majority of gastric MALT lymphoma cases. MALT lymphomas are categorized as indolent or low-grade B-cell lymphomas. Very rarely do they show features of high-grade histology or transformation at the time of initial presentation.