Patients ≥ 18 years old who have been diagnosed with appendiceal cancer with peritoneal metastases, have had cytoreductive surgery, have availability of archival tumour tissue and have consented to our institutional biobank program or have a waiver of consent for deceased patients who have not had the opportunity to provide biobank consent (requested at the time of ethics review). Descriptive analysis of the proportion of genetic mutations identified in appendiceal cancers. This is given by the percentage of pathogenic mutations in the peritoneal metastasis compared to the primary tumour.