ARID1B and neoplasm: The diagnosis was made based on a precursor lesion of the gallbladder epithelium and the presence of residual glandular tumor structures as well as a loss of SMARCA2 and mutations in PBRM1 and ARID1B. We hope that the case demonstrated here will be useful to deepen the understanding of SWI/SNF-deficient carcinomas of the gastrointestinal tract.