Appendiceal malignancy is an orphan disease encompassing a range of conditions ranging from low grade appendiceal neoplasms that may give rise to diffuse peritoneal adenomucinosis or pseudomyxoma peritonei through to frank appendiceal adenocarcinoma. Although being rare and accounting for 0.5% of all gastrointestinal malignancy there is a slowly emerging understanding of biology of this disease. Historically these conditions have been considered untreatable with curative intent due to dissemination through the peritoneal space. Both low and high-grade appendiceal neoplasm can be managed with cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy (HIPEC). With CRS and HIPEC low grade disease may achieve median survival in excess of 15 years and appendiceal adenocarcinoma may achieve 50% 5-year survival. Although in clinical practice appendiceal malignancy has been managed in a similar manner to colorectal cancer the outcomes are significantly different, even for high-grade disease. This presentation will address the emerging understanding of the biology of appendiceal neoplasms, controversies in pathological classification, developments in diagnosis and prognostic biomarkers, treatment strategies and rare pathological variants such as goblet cell adenocarcinoid tumours. The role of mucin as an anti-cytotoxic and potential new therapies will be discussed.