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Table 1 Classification of epithelial neoplasia of the appendix

From: Low-grade appendiceal mucinous neoplasm and endometriosis of the appendix

Terminology Defining factors Secondary defining factors
Adenoma Tubulor, tubulovillous, or villous adenoma with low- to high-grade dysplasia  
Low-grade appendiceal mucinous adenoma Mucinous neoplasm with low-grade cytologic atypia Presence of ≥ 1 of the following:
-Submucosa fibrosis
-Loss of muscularis mucosae
-Diverticulum-like growth through appendiceal wall
-Dissection of acellular mucin
-Mucin outside the appendix
-Appendiceal rupture
Mucinous adenocarcinoma Mucinous neoplasm with evidence of cellular invasion past the epithelial layer