title: Early low-grade gastric MALToma rarely transforms into diffuse large cell lymphoma or progresses beyond the stomach and regional lymph nodes.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pathology, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Ting-Yun
authors.initials: TY
authors.lastname: Liu
authors.forename: Pei-Han
authors.initials: PH
authors.lastname: Dei
authors.forename: Sung-Hsin
authors.initials: SH
authors.lastname: Kuo
authors.forename: Chung-Wu
authors.initials: CW
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001706:Biopsy; D002471:Cell Transformation, Neoplastic; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005753:Gastric Mucosa / Q000473:pathology*; D006785:Hospitals, University; D006801:Humans; D053208:Kaplan-Meier Estimate; D008198:Lymph Nodes / Q000473:pathology*; D018442:Lymphoma, B-Cell, Marginal Zone / Q000188:drug therapy / Q000473:pathology*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D013624:Taiwan; D016896:Treatment Outcome