Background: Cholecystectomy is a common surgical procedure and incidental gallbladder cancer is a rare and unexpected finding at a cholecystectomy performed upon benign indications. Whether to perform routine or selective histopathology of the gallbladder specimen is still a subject for discussion. The prognosis of gallbladder cancer is largely affected by tumour stage and treatment.

Aims: The overall aim was to study whether routine histological examination of the gallbladder specimen is of clinical and health economic value; determine if there are any predictive factors of incidental gallbladder cancer at benign cholecystectomy and compare the management and outcome of incidental gallbladder cancer patients in Sweden.

Methods: All studies were based on registry data from GallRiks (The Swedish Registry for Gallstone Surgery and Endoscopic Retrograde Cholangiopancreatography) between 2007 and 2016, with some modifications between studies. Complemental cross-linkage was made to national registries, and medical records were reviewed. Papers I, II and III were population-based observational studies with prospectively and retrospectively collected data. Paper IV was a health economic evaluation based on the results from papers I and III.

Results and conclusions: Hospitals submitting >75 per cent of gallbladder specimens diagnosed a higher proportion of incidental gallbladder cancer than did hospitals submitting ≤25 per cent of samples (paper I). Incidental gallbladder cancer was more prevalent in older patients, women and patients with acute or previous cholecystitis, as well as ongoing jaundice. The risk model based on predictive preoperative factors was further improved by adding a macroscopic assessment of the gallbladder (paper II). Predictive factors for gallbladder cancer appeared to have an impact on which specimens were submitted in hospitals with a selective approach of histopathology (paper I). For pT2 and pT3 patients, re-resection improved diseasespecific survival, although these groups differed in terms of age and comorbidity (paper III). Residual disease was an independent factor for impaired survival. A change to routine histopathology of gallbladder specimens in Sweden would lead to increased costs with little improved health outcomes. Instead, a more standardized approach to selective histology would be needed (paper IV).