Survival among 148 patients with an incidentally detected appendiceal tumours at surgery for acute appendicitis: a population-based cohort follow-up study

Purpose To investigate the long-term prognosis of appendiceal tumours incidentally detected at appendicectomy for suspicion of benign appendicitis. Methods A retrospective register-based single centre cohort study was carried out, using data from the local acute appendicectomy quality register of cases operated on at the Department of Surgery, South General Hospital, Stockholm, Sweden. The local colorectal cancer register was also used to identify appendix tumours. The study period was between January 2004 and January 2023. Survival was calculated according to the Kaplan-Meier method. Results A total of 11,888 patients were registered in the acute acute appendicectomy register, 54% males and 46% females, median age 32 (Q1 = 21, Q3 = 47) (with 33.7% were 41 years or older). From the appendicectomy and colorectal registers 148 (1.2% of the total cohort) appendiceal tumours were found; 60% in females and 40% in males, median age 56 (Q1 = 43, Q3 = 70) (with 78.4% being 41 years or older). Tumours found were: Low grade Appendiceal Mucinous Neoplasms (LAMN, N = 64); Neuroendocrine Tumours (NET N = 24); adenocarcinomas or other form of carcinomas (N = 57); and adenomas (N = 3). The overall 5-year survival in patients operated for LAMN was 96.8%, for NET 93.3% and for adenocarcinoma 69.7%. The overall 5-year survival for all tumour patients was 85.7%. For the younger patients (< 51 years) with LAMN and NET, almost all survived to the end of follow-up. Survival of patients in the carcinoma group was statistically significantly lower than for the LAMN and NET groups, especially in females 51 years or older. In the group of tumour patients undergoing surgery (n = 146), primary surgery was laparoscopic in 47% and open in 52%. Two patients did not undergo surgery due to widespread disease. In 64% of cases operation was acute, whereas it was delayed and/or planned in 34%. Most procedures were laparoscopic appendicectomy 36%, followed by open appendicectomy 30%, right-sided hemicolectomy 14.6% (open 11.6% and laparoscopic 3%, acute operation 5.5%), ileocaecal resection 5% (acute operation 3.4%), and staging laparoscopy 7%. In 38% of the operated patients the tumour was discovered incidentally at histopathology examination. Two patients had CRS and HIPEC as the initial operation. Forthy-three per cent of the 146 tumour patients operated underwent a second procedure: CRS and HIPEC in 23.3% and right-sided hemicolectomy in 13.6% (laparoscopic 8.2% open 5.4%). Conclusion Survival was high for patients with incidentally detected appendiceal LAMN or NET, but not so for carcinoma. Survival was lower in the carcinoma group older than 50 years, especially those sick and females.