Blood, 1 January 2002, Vol. 99, No. 1, pp. 1-1
Gastric lymphoma: a tale of 2 MALTs
Gastric lymphoma is clinically heterogeneous. While the vast
majority of cases occur in individuals infected with Helicobacter pylori, the cases can show a range of histologies and can follow diverse natural histories. Tumors may comprise mainly small cells, contain predominantly large cells with a small-cell component, or
consist entirely of large cells, similar to diffuse large B-cell lymphomas occurring in nodes or other extranodal tissues. Like follicular lymphomas, tumors in some patients start out as small-cell tumors and evolve to diffuse large B-cell lymphomas. But other patients
present with diffuse large B-cell lymphomas without any apparent
small-cell phase.
Similarly, response to therapy is heterogeneous. About half of patients
with small-cell tumors respond to eradication of H pylori. The other half do not respond to antibiotics. Some of these antibiotic-resistant patients undergo histologic
progression to diffuse large B-cell lymphoma, and some of
these patients continue to have small-cell lymphomas. Work by Starostik
and colleagues (page 3) identifies distinct genetic abnormalities in
the different tumors. These findings have important clinical implications.
Patients with gastric low-grade MALT lymphoma whose tumors do not
respond to antibiotics fall into 2 distinct classes with diverse
natural histories. Those containing the t(11;18) that deregulates
expression of API2 and MALT genes are genetically stable and highly unlikely to undergo progression to diffuse large B-cell lymphoma; about half the cases contain this translocation. By
contrast, 67% of cases not bearing t(11;18) have multiple genetic lesions most often including amplification of 3q27. Patients with concomitant small- and large-cell components almost never contain t(11;18) and nearly always contain 3q27 amplification in addition to
other abnormalities (often deletions) in 5q21, 13q14, and 17p13 regions. Thus histologic progression is a feature of genetic
instability in tumors without t(11;18).
Dan L. Longo
National Institutes of
Health
