Classification of and cytoreductive surgery for low-grade appendiceal mucinous neoplasms

Abstract

Background: Low-grade appendiceal mucinous neoplasm (LAMN) is a precursor lesion for pseudomyxoma peritonei (PMP), which, if treated suboptimally, may later disseminate throughout the abdominal cavity. The role of cytoreductive surgery for these relatively early lesions is unclear.

Methods: Clinicopathological details and treatment outcomes of patients with a LAMN and disease limited to the appendix or immediate periappendiceal tissues, referred to a national treatment centre between 2002 and 2009, were evaluated prospectively.

Results: Of 379 patients with a diagnosis of PMP, 43 (median age 49 years) had LAMNs localized to the appendix and periappendiceal tissue. Thirty-two patients initially presented with symptoms of acute appendicitis or right iliac fossa pain. Two distinct lesions were identified: type I (disease confined to the appendiceal lumen) and type II (mucin and/or neoplastic epithelium in the appendiceal submucosa, wall and/or periappendiceal tissue, with or without perforation). Type I lesions were managed by a watch-and-wait surveillance policy with serial measurement of tumour markers and computed tomography in 14 of 16 patients. Seventeen of 27 patients with type II lesions underwent risk-reducing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy with low morbidity. After a median follow-up of 40 months, there was no disease progression in either treatment pathway.

Conclusion: This study identified two LAMN subtypes. Type II lesions have pathological features of increased risk for dissemination and should be considered for risk-reducing cytoreductive surgery.