Gallbladder cancer mimicking perihilar cholangiocarcinoma—considerable rate of postoperative reclassification with implications for prognosis

Background: For some patients undergoing resection under the suspicion of a perihilar cholangiocarcinoma (pCCA), postoperative diagnosis may differ from the preoperative diagnosis. While a postoperative finding of benign bile duct stricture is known to affect 3–15% of patients, less has been described about the consequences of finding other biliary tract cancers postoperatively. This study compared pre- and postoperative diagnoses, risk characteristics, and outcomes after surgery for suspected pCCA. Methods: Retrospective single-center study, Karolinska University Hospital, Stockholm, Sweden (January 2009–May 2017). The primary postoperative outcome was overall survival. Secondary outcomes were disease-free survival and postoperative complications. Survival analysis was performed by the Kaplan–Meier method. Results: Seventy-one patients underwent resection for suspected pCCA. pCCA was confirmed in 48 patients (68%). Ten patients had benign lesions (14%), 2 (3%) were diagnosed with other types of cholangiocarcinoma (CCA, distal n = 1, intrahepatic n = 1), while 11 (15%) were diagnosed with gallbladder cancer (GBC). GBC patients were older than patients with pCCA (median age 71 versus 58 years, p = 0.015), with a large proportion of patients with a high tumor extension stage (≥ T3, 91%). Median overall survival was 20 months (95% CI 15–25 months) for patients with pCCA and 17 months (95% CI 11–23 months) for patients with GBC (p = 0.135). Patients with GBC had significantly shorter median disease-free survival (DFS), 10 months (95% CI 3–17 months) compared 17 months (95% CI 15–19 months) for patients with pCCA (p = 0.010). Conclusions: At a large tertiary referral center, 15% of patients resected for suspected pCCA were postoperatively diagnosed with GBC. Compared to patients with pCCA, GBC patients were older, with advanced tumors and shorter DFS. The considerable rate of re-classification stresses the need for improved preoperative staging, as these prognostic differences could have implications for treatment strategies.