Appendiceal Tumors: A Narrative Review

Appendiceal tumors (ATs) are classified by the World Health Organization's (WHO) 5th edition of their categorization of digestive system tumors into four subtypes: mucinous neoplasms, adenocarcinomas, serrated lesions, polyps, and neuroendocrine neoplasms (NENs). Due to their rarity and the lack of data from randomized controlled studies, ATs can be challenging to differentiate in medical practice. Specimens obtained during appendectomies for clinically acute appendicitis typically contain ATs. Most ATs in the European population affect women over 50 years. Neuroendocrine tumors (NETs) are the most common histological type, comprising 54.6%, followed by cystic, mucinous, and serous neoplasms (26.7%) and adenocarcinoma not otherwise defined (NOS) (18.6%). Most findings of ATs on pathologic investigation are benign lesions or small NENs that do not require additional treatment. The development of pseudomyxoma peritonei (PMP), a complicated situation of peritoneal carcinomatosis, may result from the presence of appendiceal mucinous neoplasm (AMN). Over the past few decades, multimodal treatment for abdominal cancers has advanced; however, ATs' clinical diagnosis and management are still debated. This review aims to outline the diagnostic options, molecular-based diagnosis, staging, treatment, and prognostic markers related to ATs.