Though LAMN can be asymptomatic and stable, it can rupture and seed mucin and neoplastic epithelium into the peritoneum, leading to pseudomyxoma peritonei (PMP), a serious complication characterized by intraperitoneal accumulation of mucinous tumors and ascites with a high morbidity and mortality rate. Here, MUC5AC is linked to pseudomyxoma peritonei.