Professor Gregory Lauwers from Moffitt Cancer Center discusses his team’s recent study comparing index and metachronous gastric cancers in 42 Korean patients. Gastric adenocarcinomas were classified into 5 subtypes: EBV-associated, MMR deficient (MMRD), E cadherin aberrant, p53-aberrant [p53(+)], and p53 non-aberrant [p53(neg)]. Although no significant difference in the frequency of most molecular subtypes was found between index and metachronous lesions, the number of MMRD gastric cancers more than doubled in the latter group. Half of the metachronous cancers had a divergent molecular subtype. The later divergence could indicate a shift in the carcinogenic mechanism affecting residual mucosa possibly related to Helicobacter pylori eradication. Study by Lauwers et al, Comparative molecular subtypes of index and metachronous gastric adenocarcinomas: a study of 42 Korean patients. Modern Pathology, 34, 1728–1737 (2021).