Low-Grade Appendiceal Mucinous Neoplasm (LAMN) Management

Definition and Pathological Features

LAMN is characterized as a mass-forming pre-invasive neoplasm that grows within the appendix with mucinous epithelium showing low-grade dysplasia 1
These tumors display simple glandular architecture with elongated and crowded neoplastic cells that maintain polarity with respect to the basement membrane 2
LAMN is distinguished from high-grade appendiceal mucinous neoplasms by the absence of pronounced nuclear atypia and loss of epithelial cell nuclear polarity 2

For LAMN confined to the appendix (Type I): Simple appendectomy is sufficient for well-differentiated tumors <1 cm with no adverse features 3
For LAMN with high-risk features (Type II): Right hemicolectomy is indicated for tumors ≥2 cm, even without obvious malignant features 3
For LAMN with high-risk features (Type II): Further resection (right hemicolectomy) should be considered if the tumor breaches the serosal surface, invades the mesoappendix by more than 3 mm, or is located at the base of the appendix 3

For patients with completely resected LAMN without high-risk features: Follow-up examinations as clinically indicated, with some institutions suggesting examination at 1 year post-appendectomy and then with decreasing frequency 4
For larger tumors or those with adverse features: Follow-up every 3-12 months for up to 10 years 3
For larger tumors or those with adverse features: Perform multiphasic CT or MRI (abdominal/pelvic) during follow-up 3
For larger tumors or those with adverse features: Consider chromogranin A as a tumor marker, particularly for neuroendocrine components 3, 4