Clinical Outcomes of Low-Grade Appendiceal Mucinous Neoplasms in a Single Institution.

OBJECTIVES: Low-grade appendiceal mucinous neoplasm (LAMN) is a rare tumor with limited malignant potential but a risk of pseudomyxoma peritonei (PMP) if perforation occurs. We aimed to characterize clinicopathological features, assess recurrence risk, and evaluate postoperative surveillance. METHODS: We retrospectively reviewed 44 patients with pathologically confirmed LAMN who underwent surgery at our institution between 2010 and 2025. Clinicopathological factors, recurrence, and surveillance strategies, including tumor markers and computed tomography (CT), were analyzed. Recurrence-free survival (RFS), overall survival (OS), and disease-specific survival were calculated. RESULTS: Median age was 64 years. Preoperative tumor marker elevation was uncommon. Risk factors included pT4 in 14 patients (33%), extra-appendiceal mucin in 1 (2.3%), positive margin in 1 (2.3%), and perforation in 15 (34.1%). Over a median 36-month follow-up, no recurrences or PMP occurred; one death from an unrelated cause was observed, resulting in 5-year RFS and OS of 97.7%. No disease-specific deaths occurred. Median annual CT frequency was 1.7 (42 mSv). The estimated annual copayment for follow-up examinations was approximately ¥7,200 per patient. CONCLUSIONS: Surgically resected LAMN showed favorable mid-term outcomes. However, given the limited follow-up and absence of events, the findings should be interpreted cautiously as preliminary insights into postoperative surveillance.