Pathological examination of the resected specimen revealed that a pyloric gland adenoma, which was positive for MUC6 and MUC5AC, had detached from its mucosal stalk, leading to significant hemorrhage. Although the primary indication for resecting large gallbladder polyps (≥10 mm) is malignancy risk, this case suggests that the risk of acute haemorrhagic complications from tumour detachment should also be recognized as a strong rationale for surgical intervention.