Extranodal marginal zone B-cell lymphoma (MALT lymphoma)

Clinical features

Lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) comprises about 7-8% of all non-Hodgkin lymphomas (NHLs). It is a neoplasm of adults with a median age at presentation of about 60 years and with a slightly higher proportion of females than males. The presenting symptoms are essentially related to the primary location. Few patients present with elevated lactate dehydrogenase (LDH) or β2 microglobulin levels. Constitutional B-symptoms are extremely uncommon. MALT lymphoma usually remains localized for a prolonged period within the tissue of origin, but dissemination to multiple sites is not uncommon and has been reported in up to one-quarter of cases, with either synchronous or metachronous involvement of multiple mucosal sites or non-mucosal sites such as the bone marrow, the spleen, or the liver. Regional lymph nodes can also be involved. Bone marrow involvement is reported in up to 20% of cases.

The stomach is the commonest localization, representing about one-third of the cases. Other typical presentation sites include the salivary glands, the orbit, the thyroid, and the lung; the frequency of occurrence in different organs is shown in Table 7.1.

Within the stomach, MALT lymphoma is often multifocal, possibly explaining the reports of relapses in the gastric stump after surgical excision. Gastric MALT lymphoma can often disseminate to the small intestine and to the splenic marginal zone. Concomitant gastrointestinal (GI) and non-GI involvement can be detected in approximately 10% of cases.