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Peritoneal Surface Malignancies

E368: Low Grade Appendiceal Mucinous Neoplasms (LAMN): Recurrence Risk and Disease Surveillance

Introduction: Appendiceal neoplasms are a rare entity, accounting for a minor fraction of colonic neoplasms; however, pathology and prognosis are diverse amongst them. Few reports examine risk factors for recurrence in relation to demographics and cytopathology. Our objective is to identify patient demographics, cytopathologic, and laboratory criteria as a means for prognostic information to guide disease surveillance and direct future studies.

Methods: A retrospective cohort study was performed that identified 150 patients with a diagnosis of appendiceal neoplasms from January 1, 2015 to January 31, 2021. All patients were required to have a pathology report for review of diagnosis. Calculation of the neutrophil-to-lymphocyte (N-to-L) and platelet-to-lymphocyte (P-to-L) ratio was performed.  

Results: Pathology groups were split into the following: Low grade appendiceal neoplasm (LAMN); High grade appendiceal neoplasm (HAMN); and Mucinous adenocarcinoma. Demographics were examined and 62% of patients identified with a mucinous appendiceal lesion were female and >50 years old. Nine patients were identified as having a recurrence, with the following clinically significant risk factors: histology type, presentation with perforation, histologic grade, mucin composition, tumor deposits, pT4 lesions, and M1 disease. Recurrence was present in 3 patients with LAMN, 1 patient with HAMN, and 5 patients with mucinous adenocarcinoma. Interestingly, of the three patients with LAMN whom recurred all patients had a pT4 lesion at diagnosis. Yet, 21 LAMN patients were identified having a pT4 lesion representing only 14% of those patients having a recurrence, which typically occurred within two years from diagnosis. Our study was unable to identify any clinical significance of a high N-to-L ( >3) or P-to-L ( >300) ratio correlating to a risk of recurrence. However, p</span>atients with mucinous adenocarcinoma that developed recurrence all had evidence of high N-to-L ratios highlighting the need for further studies examining the application of this as a surveillance tool. 

Conclusions: Patients with LAMN without evidence of perforation, less than T4 lesions, and without mucin deposits are low risk for recurrence and should be considered “surgically complete.” We recommend no surveillance imaging of these patients, and follow-up only for symptom development. Next steps will involve a multi-institutional review of patient data exploring these factors and the recurrence risk

Learning Objectives:

  • Describe risk factors for recurrence in patients with low grade appendiceal neoplasms.
  • Define the percent risk of recurrence in patients with low grade appendiceal neoplasms that have associated risk factors.
  • Develop a surveillance recommendation plan for patients with low grade appendiceal mucinous neoplasms with and without risk factors for recurrence.