Risk of malignancy in Caroli disease and syndrome: A systematic review

BACKGROUND Congenital intrahepatic bile duct dilatation without fibrosis is called Caroli disease (CD), and is called Caroli syndrome (CS) when it has fibrotic and cirrhotic liver morphology. The development of intrahepatic carcinoma is described in both conditions, but the reported incidence varies extensively. Potential risk factors for the malignant transformation were not described. Furthermore, conservative or surgical treatment is performed depending on the extent of cystic malformation, hepatic dysfunction and structural hepatic changes, but little is known about which treatment should be offered to patients with CD or CS and cancer. AIM To further investigate the malignant transformation in these conditions. METHODS A systematic review of the current literature until January 2019 was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. A search using Medline (PubMed) was performed using a combination of Medical Subject Headings terms "caroli disease", "caroli syndrome", "tumor", "malignant", and "cholangiocarcinoma". Only human studies published in English were used for this systematic review. The following parameters were extracted from each article: year of publication, type of study, number of patients, incidence of malignant tumor, duration of symptoms, age, sex, diagnostics, identification of tumor, surgical therapy, survival and tumor recurrence. RESULTS Twelve retrospective studies reporting the courses of 561 patients (53% females) were included in this systematic review. With a mean age of 41.6 years old (range 23 to 56 years old), patients were younger than other populations undergoing liver surgery. Depending on the size of the study population the incidence of cholangiocarcinoma varied from 2.7% to 37.5% with an overall incidence of 6.6%. There were only few detailed reports about preoperative diagnostic work-up, but a multimodal work-up including ultrasound of the liver, computed tomography, magnetic resonance imaging and endoscopic retrograde cholangiopancreatography was used in most studies. Disease duration was variable with up to several years. Most patients had episodes of cholangitis, sepsis, fever or abdominal pain. Tumor detection was an incidental finding of the surgical specimen in most cases because it is currently often impossible to detect tumor manifestation during preoperative diagnostics. Liver resection or liver transplantation was performed depending on the extent of