Molecular Aspects of H. pylori-Related MALT Lymphoma

Abstract

Helicobacter pylori-related extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue is a paradigm for malignancy arising in an inflammatory background. While the diagnosis of H. pylori gastritis is often straightforward, distinction between severe gastritis and early lymphoma can be difficult and requires careful assessment of clinical findings in addition to histological features and immunohistochemical results. A number of cytogenetic abnormalities have been discovered in H. pylori-related lymphomas and several have clinical importance, related to the responsiveness of lymphoma to H. pylori eradication therapy, but routine molecular studies are not widely utilized. While molecular methods may be used in equivocal cases, a trial of conservative therapy is warranted given the propensity for these lymphomas to regress with eradication of the organism. Once therapy is initiated, care must be taken to avoid a premature assignment of disease refractoriness because complete response can take several months to more than a year. Cases truly refractory to H. pylori eradication therapy may be treated with adjuvant chemoradiation with a high response rate.

Figure 1

Helicobacter pylori, the underlying cause of most cases of gastric MALT lymphoma. The curved bacteria are seen in the surface mucus layer of the gastric pits and have a characteristic, curvilinear, “gull-wing” appearance (600x original magnification).

Figure 2

MALT lymphoma. The histomorphology in this case closely resembles severe H. pylori gastritis. Note the infiltration of the muscularis mucosae at the base of the mucosa (arrows). The clinical information was crucial in this case, as diffusely thickened gastric folds were seen endoscopically (400x original magnification).

Figure 3

Lymphoepithelial lesions. This infiltration and destruction of the gastric gland epithelium by lymphocytes is a characteristic, but not specific, feature of MALT lymphoma (400x original magnification).