A choledochal cyst is a cystic dilatation of the biliary tree and a well-known cause of biliary tract malignancies.123 It is a relatively rare disease; incidence rates ranging from 0.32% in Asia and 1 in 13,000 to 1 in 2 million births in western countries.34 Most cases are diagnosed during early childhood, but between 20% to 30% of cases are first detected in adults as choledochal cyst either causing symptoms or found incidentally during imaging for an unrelated cause.4 It has been reported that only a small number of patients who underwent surgical management for choledochal cyst had progression to biliary malignancy.5 The incidence of cancer in patients with primary choledochal cyst is 9.9%, whereas the incidence of cancer development after cyst excision is 0.6%.6 Herein, we present a case of a patient who had been treated for choledochal cyst in an alternative manner with no follow-up, which then progressed to cholangiocarcinoma.

A 46-year-old woman visited Busan Paik Hospital Hepatobiliary clinic with dyspepsia and right, upper quadrant, abdominal pain. The patient had a history of a cystoduodenostomy nearly 35 years ago. There was a palpable mass in her abdomen in the right, upper quadrant. Initial laboratory findings were as follows: total bilirubin 0.5 mg/dl, aspartate transaminase/alanine transaminase 16/14 IU/L, alkaline phosphatase 276 U/L, alpha-fetoprotein 2.01 ng/ml, carcinoembryonic antigen 0.756 ng/ml, carbohydrate antigen 19-9 11.70 U/ml, and hepatitis B surface antibody-positive. Abdomino-pelvic computed tomogram (APCT) scan and magnetic resonance cholangiopancreaticography (MRCP) showed moderate central dilatation of the intrahepatic duct with pneumobilia and a large, cystic, mass-like lesion with internal echogenicity and probable bezoar formation within a choledochal cyst of 6.8 cm×8.5 cm×5.0 cm in size (Fig. 1). There was also mild proximal pancreatic duct dilatation with lobulated mass suggestive of intraductal papillary mucinous neoplasm. Her esophagogastroduodenoscopy showed an opening, at the second portion of the duodenum,with gastritis.

The initial plan for the operation was to undergo revision of the cystoduodenostomy and/or cyst excision with a hepaticojejunostomy. Because of the bezoar-like mass in the cyst, the patient was in a fasting state for 2 days prior to surgery, hoping that the mass would be dismantled. An incision was made via the previous right paramedian scar. Underneath the scar there was a severe adhesion so adhesiolysis was performed. The previously performed cystoduodenostomy was identified with multiple lymph node enlargement near the superior mesenteric vein and stomach. A small portion of the common bile duct was excised for frozen biopsy, which revealed adenocarcinoma; moreover, cystic dilatation had extended to the pancreas because of an anomalous pancreaticobiliary ductal union (APBDU). Thus, a pancreaticojejunostomy was inevitable for complete excision of the cyst and proper management for cholangiocarcinoma. Within the cyst, there was a mass: a conglomeration of food material with bile. A cholecystectomy, subtotal gastrectomy, pancreaticojejunostomy, and gastrojejunostomy were performed. The patient's extrahepatic bile ducts were unusually low-lying, so the surgeon performed a ductoplasty, conjoining the left and right extrahepatic bile ducts side to side, making it easier to carry out hepaticojejunostomy.

The final pathology report proved the presence of adenocarcinoma: moderate differentiation arising in the choledochal cyst, invading to surrounding adipose tissue (pT2a), accompanying severe inflammatory infiltration, and one metastatic lymph node out of seven excised lymph nodes, stage IIB (Fig. 2). It has been nineteen months since the patient had her surgery and she is going through oral doxifluridine chemotherapy without any complications or recurrences to date.

Choledochal cysts are congenital anomalies of the bile ducts, which are subdivided into five different categories. The most common types are I and IVa, the dilatation of the extrahepatic bile duct and both the extrahepatic and intrahepatic bile ducts, consecutively. Asians and women tend to have a higher incidence than Caucasians and men, though clear reasons for these tendencies are yet to be elucidated.2 In many cases, diagnosis is made early during childhood in 80%; however, due to the advance of imaging techniques, some diagnoses are incidentally made in adulthood.4 Symptom triads are abdominal pain, jaundice, and an abdominal mass, but only rarely do these symptoms coexist. Treatment of choice is a total cystectomy and Roux-en-Y hepaticojejunostomy; less frequently, cystoenterostomy has been used as an alternative method.1 The standard form of surgery prevents subsequent complications such as pancreatitis, cholangitis, portal hypertension and malignancy. The risk of cholangiocarcinoma in a choledochal cyst is as high as 20-30% in early adulthood if no surgical intervention is performed. On the other hand, cholangiocarcinoma following a choledochal cyst resection is relatively rare, with an incidence rate of 0.7-6%.5

The exact pathophysiology of cholangiocarcinoma in a choledochal cyst is still unknown, but it is suspected that the reflux of pancreatic juice is the main cause, promoting chronic inflammatory changes and carcinogenesis.3 This patient had a Type I choledochal cyst and, due to a previous cystoduodenostomy, not only pancreatic juice but also food material had refluxed into the biliary tract, causing bezoar formation and eventually malignancy. Previous studies have emphasized the necessity of long-term follow-up for patients who have had a cyst excision, since it is known that the risk of biliary malignancy in the remnant bile duct increases more than 15 years after surgery, as in the case of our patient.5 For those who had a cystoenterostomy, 78 it is mandatory that they have regular check-ups since the incidence rate of malignancy or complications such as cholangitis, hepatolithiasis, and pancreatitis could be as high as 70%.1

In conclusion, it should be emphasized that the standard treatment of choledochal cyst is complete cyst excision and hepaticojejunostomy. If for some reason this is not possible, a cystoenterostomy can be an alternative treatment, but meticulous life-long follow-up is essential for early detection and management of complications.