OBJECTIVETo explore the pathological features and prognosis of appendiceal mucinous neoplasms (AMN) based on WHO classification 2010.

METHODSSeventy consecutive cases of AMN were classified into 5 groups according to WHO classification of digestive system tumors in 2010 including mucinous adenomas/cystadenoma (MA), low grade appendiceal mucinous neoplasms (LAMN), low grade pseudomyxoma peritoneum originated from appendix (PMP-L), invasive mucinous adenocarcinomas (MAC) and high grade pseudomyxoma peritoneum originated from appendix (PMP-H). Clinicopathological features, classification, treatment and prognosis of AMN were investigated retrospectively.

RESULTSThere were 11 cases of MA with neoplastic epithelium and mucin being defined in lumen and mucosa but without invasive lesions, and no relapse or death was found. In 41 LAMN cases, mucin was found in submucosa, muscularis proparis, or serosa of appendix, no or only scant mucinous epithelium with low grade dysplasia presented in mucinous pools in most cases (39/41). Among 41 LAMN cases, 3 developed relapse or PMP-L, and no death was observed. In 7 PMP-L cases, low grade dysplastic mucinous epithelium in mucinous pools could be found easily in 3 cases and was very scanty in 4 cases, with 1 relapse and 1 death. Eleven invasive carcinomas were found, including 7 MAC cases and 4 PMP-H cases, with local high grade dysplastic epithelium at least. In these invasive lesions, 4 cases recurred and 3 case died (including 2 recurred cases above). MA and LAMN were both non-invasive neoplasms histologically, however, PMP-L, MAC and PMP-H were regarded as adenocarcinomas according to their biological behavior.

CONCLUSIONAMN displays a relatively homogeneous group of neoplasms that pursues a predictable clinical course based on their nature, so it is necessary to diagnose and administrative accurately with consistently standards for these neoplastic entities.