Risk stratification of surveillance for low-grade appendiceal mucinous neoplasms

Low-grade appendiceal mucinous neoplasms (LAMNs) can progress to pseudomyxoma peritonei (PMP). The incidence and risk factors for recurrence are unclear, and there is a lack of consensus on the need and duration of surveillance imaging.

Patients at the Mayo Clinic in Rochester, Minnesota, with a histologic diagnosis of LAMNs confined to the appendix and limited involvement of the right lower quadrant from 1992 to 2023 were included. Associations between recurrence and risk factors were assessed using Kaplan-Meier curves and Cox proportional hazards regression.

A total of 125 patients with LAMNs underwent abdominal imaging surveillance for a median of 51.2 months (IQR, 26-92). Of note, 5 patients (4%) recurred, all of which were PMP. Overall, the 5- and 10-year cumulative recurrence incidence rates were 3% and 6%, respectively. The median time to recurrence was 24 months (IQR, 23-87). Only LAMNs limited to the right lower quadrant and LAMN tumor size of <2 cm were associated with recurrence (P < .05). The 5- and 10-year cumulative recurrence risks were 12% and 30%, respectively, for the 21 patients with either risk factor. Only 1% of patients without these 2 risk factors developed a recurrence at 10 years.

The overall recurrence risk of LAMN after resection is low. Appendectomy is sufficient for LAMN. Select patients with acellular mucin confined to the right lower quadrant and a tumor size of <2 cm are at higher risk of recurrence. Thus, long-term surveillance is recommended for high-risk individuals. Conversely, LAMNs without risk factors can be safely observed expectantly.