Low-grade Appendiceal Mucinous Neoplasm: A Clinicopathological Study of 38 Cases

Introduction: Low-grade appendiceal mucinous neoplasm (LAMN) is a rare, yet clinically significant entity. LAMN lack the potential for haematogenous metastasis. It can disseminate in the peritoneum, depositing extracellular mucin and epithelium along peritoneal surfaces, causing Pseudomyxoma Peritonei (PMP). It is important to differentiate LAMN from mucocoele, serrated lesions, adenomas and mucinous adenocarcinoma. Thorough histopathological evaluation is important in the differentiating these entities. Aim: To analyze the clinicopathological features of LAMN. Materials and Methods: This is a cross sectional study, included all cases reported as LAMN in 8 years (from 1 January 2016 to 31 December 2023) from Regional Cancer Centre, Thiruvananthapuram, Kerala, India. Clinical findings, radiological features, gross findings and detailed histopathological features were analysed.Descriptive statistical analysis was performed to summarise the clinicopathological characteristics. Results: Total number of cases in the present study were 38.The mean age at diagnosis was 48 years,with a slight female predominance (M:F=1:1.3). Abdominal pain was the most common presenting symptom 24 (63.16%). The average tumour size of appendiceal mass lesions was 4.5 cm.Histopathologicalfindings demonstrated variable epithelial architecture-epithelialdenudation 32 (84.21%), villiform proliferation 22 (57.89%), flat epithelium 16 (42.11%) - with low gradenuclearatypia. On thebasis of the American Joint Committee on Staging eighth edition cancer staging manual, 24 (63.15%) of cases were categorised as pTis, 2 (5.26%) as pT3, and 12 (31.57%) as pT4.Pseudomyxoma Peritonei (PMP) was observed in 8 (21.05%) patients. Concurrent ovarianinvolvement was identified in 3 (7.89%) patients. These findings underscore the propensityof LAMN for peritoneal dissemination. Conclusion: Given its potential for progression to PMP and metastasis, meticulous histopathological evaluation is essential for accuratediagnosis and risk stratification. This study highlights the necessity of a multidisciplinaryapproach in diagnosing and managing LAMN, incorporating surgical, radiological, andpathological expertise.