Clinicopathological features of non-carcinoid malignant epithelial appendix tumors and risk factors for recurrence, single-center experience.

Background: Non-carcinoid appendix epithelial tumors are rare. These tumors include low-grade and high-grade mucinous neoplasm also adenocarcinomas. We aimed to investigate the clinicopathological features, treatment, and risk factors of recurrence.

Methods: Patients diagnosed between 2008 and 2019 were retrospectively analyzed. Categorical variables were expressed as percentages and compared using the Chi-square test or Fisher's exact tests. Overall survival and Disease-free survival of the groups were calculated by the Kaplan-Meier method, and the log-rank test was used to compare the survival rates.

Results: A total of 35 patients were included in the study. Of the patients, 19 (54%) were women and the median diagnosis age of patients was 50.4 years (19-76). As for pathological types, a total of 14 (40%) patients were mucinous adenocarcinoma and 14 (40%) patients were Low-Grade Mucinous Neoplasm (LGMN). Lymph node excision and lymph node involvement were 23 (65%) and 9 (25%) patients respectively. The majority of patients were stage 4 (27, 79%) and 25 (71%) of these patients had peritoneal metastasis. A total of 48.6% patients had been treated with cytoreductive surgery and hyper-thermic intraperitoneal chemotherapy. Median Peritoneal cancer index value was 12 (2-36). The median follow-up time was 20 (1-142) months. Recurrence developed in 12 (34%) of patients. When risk factors for recurrence are considered, there was a statistically significant difference in appendix tumors with high-grade, adenocarcinoma pathology, ones with peritoneal cancer index ≥12 and not having pseudomyxoma peritonei. Median disease-free survival was 18 (13-22, 95% CI) months. Median overall survival could not be reached while the 3-year survival rate was 79%.

Conclusion: The risk of recurrence is higher in high-grade appendix tumors, having peritoneal cancer index ≥ 12, not having pseudomyxoma peritonei and adenocarcinoma pathology. High-grade appendix adenocarcinoma patients should be followed closely for recurrence.