Endoscopic morphology of gastric MALT lymphoma correlate with API2/MALT1 fusion and predict treatment response after helicobacter pylori eradication.

Background: The presence of API2/MALT1 fusion in gastric mucosa-associated lymphoid tissue (MALT) lymphoma predicts poor response to Helicobacter pylori (Hp) eradication therapy. This study aimed to assess the correlation between endoscopic morphology of MALT lymphoma and API2/MALT1 fusion and evaluate treatment response to Hp eradication based on morphological subtypes.

Methods: A retrospective review was conducted on patients diagnosed with gastric MALT lymphoma between January 2011 and December 2022. Endoscopic morphology was categorized as superficial, non-superficial, or mixed type. The superficial type was further classified into gastritis superficial lesion and localized superficial lesion based on border clarity. Logistic regression models evaluated the impact of clinical and endoscopic characteristics on anti-Hp therapy effectiveness.

Results: Among the 114 patients included, 93 (81.6%) were Hp-positive, and API2/MALT1 fusion was detected in 58 (50.9%) cases, The superficial type was the predominate morphology (73/114, 64%). The regular arrangement of collecting venules (RAC) sign was noted in 21 (18.4%) cases. In superficial subtypes, the RAC signs were more frequently observed in localized lesion than gastritis lesion (35.6% vs. 7.1%, p = 0.01). and the superficial localized lesion was more common in individuals with positive API/MALT1 fusion than negative ones (76.9% vs. 44.1%, p = 0.01). Following Hp eradication, the remission rate for localized lesion was 34.3%, significantly lower than for gastritis lesion (66.7%, p = 0.01). Both endoscopic morphology (OR = 0.26, 95% CI 0.09-0.75) and API2-MALT1 fusion (OR = 14.29, 95% CI 4.19-48.67) impacted the efficacy of anti-Hp therapy. However, multivariate analysis identified API2-MALT1 fusion as the only independent predictor of treatment outcome (OR = 12.18, 95% CI 3.49-42.55, p < 0.001).

Conclusion: Gastric MALT lymphomas with superficial-type morphology, particularly those with defined borders resembling early gastric cancer, were associated with API2/MALT1 fusion and a lower remission rate after Hp eradication therapy. This suggests that endoscopic morphology, along with API2/MALT1 fusion status, could help predict the therapeutic response, with API2/MALT1 fusion serving as a critical indicator of treatment resistance.