In an area of
lymphoma classification still being defined, marginal-zone
lymphomas have distinctive immunohistochemical and cytogenetic features that distinguish them from mantle-cell and
follicular lymphomas. There are three subtypes: the extranodal mucosa-associated lymphoid tissue (
MALT) lymphomas, the nodal monocytoid B-cell (MBCL)
lymphomas, and the splenic marginal-zone
lymphomas. The
MALT lymphomas represent the neoplastic counterpart of the gut-associated lymphoid tissue, which extends from the jejunum to the rectum. They arise in sites usually containing no lymphoid tissue, such as the stomach, thyroid, and salivary gland. Gastric
MALT lymphomas, the most common, are associated with Helicobacter pylori. The MBCL
lymphomas closely resemble
MALT lymphomas and unlike other non-Hodgkin's
lymphomas are commonly composite.
Therapy for these
lymphomas may include
radiation therapy or surgery when disease is of limited extent. However,
gastrectomy for gastric
MALT lymphomas is not in favor because of the efficacy of
antibiotic regimens that can eliminate H. pylori
infection.
Splenectomy may be indicated for splenic
lymphomas.
Purine analogs are promising therapeutic agents because they are specific for lymphoid cells. Also, they may prove useful in indolent
cancers such as these, because of their activity against dividing and resting cells.
Purine analogs may be considered as second-line
therapy after
alkylating agents for these
lymphomas.