Bile duct papilloma is a benign tumor of bile duct epithelium, which is rare clinically but seems to be increasing in recent years. Most cases have a long history of chronic cholangitis, some up to 20 years, and the jaundice manifested by bile duct papilloma has certain characteristics. Intermittent and self-limiting. Bile duct papillomatosis is a disease of bile duct papillary tumors. Bile duct papillary tumors are a group of benign and malignant papillary tumors occurring in the hepatic bile ducts, and are not uncommon clinically. Biliary duct papillomatosis is rare, but the number of reported cases is gradually increasing, with a male to female ratio of about 2:1 and an average age of 63 years. Due to the difficulty of preoperative diagnosis and the lack of uniformity in the name of the disease, some clinical reports have combined the analysis of papillary tumors in the bile duct. This disease was first described in detail by Caroli in 1959, and the etiology and pathogenesis are still unclear, with some reports in the literature relating it to biliary stones, inflammation, congenital common bile duct cysts, and abnormal pancreaticobiliary collaterals. The papillae of bile duct papillomatosis are multiple and widespread and can be diffusely distributed throughout the biliary system or confined to a specific site. Due to the obstruction of the corresponding bile ducts, regional bile duct dilatation is observed, with multiple dilated bile ducts and mucus-like bile in some patients. The lesion is well-defined and shows no signs of peripheral infiltration, and does not infiltrate the duct wall or surrounding liver tissue. The mass was a true papillary structure located in the dilated bile ducts with slender, branching papillae. The covered epithelial cells were highly columnar, with slightly eosinophilic cytoplasm and oval-shaped nuclei located in the center of the cells. The liver tissue was scattered with dilated bile ducts of varying sizes and containing papillary masses. The local epithelial cells showed atypical, rod-shaped nuclei with distinct nucleoli. The lesions may be surrounded by fibrous tissue hyperplasia, inflammatory cell infiltration, and small focal intrahepatocellular biliary sludge. There may be mild cirrhosis in the local liver tissue. The distinction between malignant intra-biliary papillomatosis and malignant tumors such as bile duct papillary carcinoma remains to be explored. It is generally accepted that patients with malignant bile duct papillomatosis should have benign papillae present. Patients with bile duct papillary carcinoma may have similarities with bile duct papillomatosis in general morphology, but histologically the papillae should be malignant and have the same pathological features. 2.Clinical manifestations Biliary papillomatosis is reported in clinical cases aged 6-83 years, and the incidence is not yet known. The incidence is not known. It is common for both internal and external bile ducts to be involved. The early clinical manifestations of bile duct papillomatosis are atypical and mainly consist of gastrointestinal symptoms, such as epigastric discomfort, vague pain, poor appetite, aversion to oil, belching and so on. As the disease progresses, acute cholangitis, jaundice and epigastric pain may occur due to partial or intermittent obstruction of the bile duct by the tumor or its necrotic and exfoliated tissues as well as excessive mucus secretion, which may be accompanied by fever. If the lesion is extensive, biliary cirrhosis, portal hypertension and liver failure may develop in the late stages due to recurrent cholangitis. Patients with combined biliary bleeding may present with significant abdominal pain and blood in the stool, but this is rare clinically. In a few patients, pancreatitis is induced by obstruction of the duodenal papilla by mucus, tumor necrotic dislodged tissue, and blood clots. In patients with malignant bile duct papillomatosis, local and distant metastasis and even malignant fluid may occur. 3.Diagnosis Because of the non-specific clinical manifestations, preoperative diagnosis of biliary papillomatosis is difficult. Most of the patients are further examined because of abnormal dilatation of the bile ducts during physical examination or when they visit the doctor for gastrointestinal symptoms. Blood tests are non-specific, mostly due to biliary obstruction and bleeding, such as elevated transaminase, alkaline phosphatase, glutamyl transpeptidase, bilirubin, etc. Occasionally, amylase may be elevated. The tumor markers CEA and CA199 may be elevated. Routine ultrasound, CT and MRI examination mostly indicate dilated bile ducts inside and outside the liver, and intra-biliary tumors are not easily detected. It may show a well-defined substantial mass extending into the dilated bile ducts inside and outside the liver, and the enhanced mass may have irregular enhancement, and the complete bile duct wall can be seen, which can be distinguished from bile duct cancer. MRCP can reveal a diffuse growth pattern, filling the bile duct system, with the duct wall still visible, which some authors call dendritic growth, and is considered a characteristic manifestation of the disease. The bile ducts are filled with irregular, flocculent floating filling defects, but are affected by stones, inflammation, blood clots, air bubbles, etc. If jelly-like mucus is found in the duodenal papilla during the examination, this disease should be considered as a possibility. Intraoperative cholangioscopy allows direct visualization of the biliary tract and helps in the diagnosis of this disease. Intraoperative rapid pathological examination has some value, but sometimes it is difficult to confirm the diagnosis. 4.Treatment Biliary papillomatosis is mainly treated surgically, because the disease is multiple, widespread, easy to malignant, high recurrence rate, treatment is more difficult. For patients with limited disease, the bile ducts and liver tissues of the lesion can be removed together to achieve the purpose of radical treatment. If the lesion is too extensive for radical resection, bile duct-jejunum Roux-en-Y anastomosis can be considered. Electrocoagulation cautery, laser tumor resection, and argon ion beam coagulation of the tumor under cholangioscopy are effective treatments. For patients with extensive, multiple involvement of the left and right lobes of the liver and difficult to completely resect the lesion, liver transplantation is the only possible radical cure. For patients with poor general condition or those who refuse surgery, ERCP and nasobiliary drainage can be performed, and internal stenting of bile ducts can be tried. For patients with co-infection, antibiotic control of infection is an effective treatment. For patients with malignant bile duct papillomatosis, radical or palliative surgery can be performed if possible. There is a lack of effective evaluation for radiotherapy and chemotherapy. 5.Prognosis Biliary papillomatosis should be generally considered as benign disease, but its recurrence rate and malignant rate are high, English literature shows that its malignant rate is 41%, therefore, some scholars consider this disease as precancerous. The patient’s prognosis depends on the ability to perform radical surgery, which has a significantly longer mean survival than palliative surgery patients. One report showed that the five-year survival rate of radical resection patients was 81%, and the average survival of patients with palliative surgery was 37 months. Also, the non-mucus-secreting type was superior to the mucus-secreting type in terms of treatment outcome.