Background: Appendix goblet cell adenocarcinomas (GCA) are rare aggressive tumours with patients often presenting with peritoneal metastases. Cytoreductive surgery and heated intraperitoneal chemotherapy (CRS/HIPEC) can be curative treatment and the role of systemic chemotherapy less defined. There is a need to better understand factors that predict outcome alongside assessment of the latest WHO 2019 classification. Methods: Demographics, clinicopathological variables, treatment characteristics and survival of patients with GCA from a UK peritoneal tumour centre were identified through a prospective database (2005-2021). Patients were selected for CRS/HIPEC based on disease burden. Pathology records were reviewed and those previously classified by Tang grading were reclassified to WHO 2019. The primary endpoint was overall survival (OS). Analysis was by the Kaplan-Meier method. Results: We identified 177 patients with GCA who had a median follow-up of 67 months (m, 4-207). Mean age at diagnosis was 57 years (22-79) and 88 were female (50%). There were 99 patients (56%) who had localised disease (M0) and 74 (42%) who had metastatic disease (M1). There were 126 (71%) patients who had CRS and 115 (91%) had HIPEC (65% MMC, 25% Oxaliplatin); median peritoneal cancer index score was 1 (0-28) and 12 (10%) patients had M1 disease. There were 72 (41%) patients who had systemic chemotherapy (72% oxaliplatin with fluoropyrimidine) and of those who had CRS, four had neoadjuvant, 18 adjuvant and the rest palliative intent chemotherapy. Incomplete CRS resulted in shorter OS compared to complete CRS (median 23 v 103m, p<0.001). Patients with involved nodes had shorter OS (32m v not reached, NR, p<0.001) compared to those with uninvolved nodes. WHO 2019 grade 2 predicts for longer OS than Tang B (median 118 v 54m, p=0.031). The table shows univariate survival according to grade and chemotherapy. Conclusions: This study represents the largest series of pure appendix GCA with long term follow-up data. Patients with positive lymph nodes and incomplete CRS had poor survival outcomes. The WHO 2019 classification had no direct prognostic correlation with the previous Tang classification. WHO 2019 grade 2 had longer OS compared to Tang B suggesting further stratification of the grade 2 group could be considered. Patients who had systemic chemotherapy had shorter OS and DFS as expected based on the selection of patients with higher grade, lymph node involvement and higher disease burden as part of clinical practice.