Early low-grade gastric MALToma rarely transforms into diffuse large cell lymphoma or progresses beyond the stomach and regional lymph nodes.

BACKGROUND/PURPOSE: Gastric mucosa-associated lymphoid tissue lymphoma (MALToma) usually presents at an early stage involving only the stomach and/or regional lymph nodes. Although a sequential transformation from low-grade gastric MALToma (GM) to high-grade GM to secondary diffuse large B-cell lymphoma (DLBCL) is commonly assumed, documented cases of transformation are rare. We aim to determine the frequency of transformation.

METHODS: We identified 55 early low-grade GMs, 18 early high-grade GMs, and 13 advanced GMs at the National Taiwan University Hospital from 1995 to 2005. The median follow-up time was 59 months.

RESULTS: We found that only one early low-grade GM and two early high-grade GMs transformed into secondary DLBCLs and progressed outside the stomach and regional lymph nodes. Significantly, we identified 13 low-grade GMs that were refractory to Helicobacter eradication therapy or relapsed after initial response. All 13 cases had been followed-up for at least 3 years without development of secondary DLBCLs. The frequency of transformation for early low-grade GM was less than 2% (1/55). Although two lymphoma-unrelated mortalities were identified, none of the 55 patients with early-low grade GMs died of the disease.

CONCLUSION: Compared with chronic lymphocytic leukemia, which has a 16% transformation rate and a median transformation time of 24 months, we conclude that early low-grade GM rarely transforms into secondary DLBCL or progresses beyond the stomach. Without transformation or progression, patients with early low-grade GM rarely die of the disease and should be treated conservatively.