choledochal cysts are rare benign cysts originating in the biliary tree historically prevalent in children , females and the japanese population . incidence of cyst disease varies from as common as 1 in every 13,000 to 1 in 2 million ( 1 ) . the longer these cysts remain in place and are allowed to grow , the higher the risk of developing a malignancy . here we present a case report of a 26 year old female with a long standing cholangiocarcinoma in a longstanding choledochal cyst . a case of cholangiocarcinoma in an unresected choledochal cyst with local invasion into pancreas and lack of nodal involvement in a total of 10 resected lymph nodes is presented . a 26 year old female presented to our surgical oncology clinic for evaluation of a type i choledochal cyst . the cyst was identified incidentally by ultrasound seven years prior during the patient s first pregnancy . a computed tomography ( ct ) scan demonstrated a 3 cm x 8 cm dilated bile duct . a magnetic resonance cholangiopancreatogram ( mrcp ) was performed and demonstrated a fusiform dilation of the extrahepatic common bile duct measuring at least 7.4 x 4.8 x 6.2 centimeters and enhancing soft tissue polypoid mass arising from the medial wall of the cyst that is concerning for malignancy but no sign of metastatic disease ( see figure 1 ) . resection was recommended at the time but patient opted to monitor growth and delayed surgery . she denied jaundice , acholic stools , vomiting , nausea or fever but did report occasional left upper quadrant pain . a repeat mri ( magnetic resonance image ) in 2011 demonstrated a seven centimeter fusiform choledochal cyst abutting the pancreas with an aberrant pancreatic duct and a concerning solid component at the anteriomedial aspect of the cyst . mrcp shows a fusiform dilation of the extrahepatic common bile duct measuring 7.4 x 4.8 x 6.2 cm in the axial ( a ) and transverse planes ( b ) . there is an enhancing soft tissue mass with a thickness of 1.1 cm protruding into the lumen of the cyst that is concerning for malignancy she underwent a trans - abdominal resection of choledochal cyst with roux - en y hepaticojejunostomy , open cholecystectomy and liver biopsy . the cyst measured seven centimeters at largest diameter and was classified as type i ib ( a choledochal cyst with focal dilation of extra hepatic biliary tree ) . the patient did not have any postoperative complications and was discharged on postoperative day four . final pathology results revealed an adenocarcinoma with focal squamous differentiation ( see figure 3 ) . the tumor was classified as pt3 as the pancreas had focal invasion with negative margins . as she had no evidence of metastatic disease , her ajcc stage was pt3n0m0 ( stage iia ) . she was enrolled into a phase ii clinical trial for chemotherapy and mindfulness relaxation which includes four cycles of gemcitabine/ capecitabine followed by radiotherapy with concurrent capecitabine . cholangiocarcinoma is a complication of choledochal cysts due to chronic mucosal irritation and the risk is increased if prior drainage procedures performed prior to cyst excision ( 2 ) . while the most common presentation has been in female infants in the past , more disease is being reported in individuals 18 and older . there is no clear etiology of the disease in adults but an anomalous junction between the bile duct and pancreatic duct is a common finding ( 2 ) . choledochal cysts that go untreated increase the risk of harboring a cholangiocarcinoma ( 1 ) . children usually present with a triad of symptoms- jaundice , abdominal mass and pain . in comparison , adults often present with abdominal pain and are thought to have pancreatitis or biliary tract symptoms and diagnosis is often delayed due to nonspecific and intermittent symptomatology ( 3 ) . preferred treatment for both groups is excision of the cyst and biliary reconstruction ( 1 ) . drainage of the cysts is no longer preferred due to reports of complications ( 4 ) . the standard treatment for type i choledochal cysts is total excision in part , due to the possibility of carcinoma developing in the cyst and in part to avoid stricture formation ( 4 - 6 ) . the percentage of patients found to have cholangiocarcinoma after excision varies from 9.7% to 25% , strongly supporting that complete and aggressive resection is warranted ( 3 ) . the most common cysts in adults are type i cysts ( dilation of extrahepatic bilary tree ) followed by type iv ( dilations of intrahepatic and extrahepatic biliary tree ) ( 1 ) . while the surgical treatment may differ based on the type of cyst , no specific cysts type has been reported to indicate a higher risk of developing into cancer . if left untreated , the risk malignant transformation increases proportionally with the time elapsed since initial choledochal cyst diagnosis ( 7 ) . edil et al reported the largest series of choledochal cyst in north america ; out of 73 adults , 4 harbored malignancy with two having cholangiocarcinoma with tumors smaller than 5 centimeters . of these two , one had lymph node involvement while the other did not ( 8) . of the few cases of choledochal cyst excision that have been reported in pregnant women , elective caesarian sections were performed to avoid stress and possible complications that the cyst could cause during labor and vaginal birth ( 9 ) . our patient s cyst was discovered incidentally during her first pregnancy and she opted to wait to have it removed afterwards and had another child before having this cyst removed . however , no complications associated with her cyst were reported during either of her pregnancies . in addition to complete resection , treatment options include radiotherapy and chemotherapy . in recent years , gemcitabine - based chemotherapy has had positive effects on improving the rate of survival in more advanced cases of cholangiocarcinoma ( 10 ) . currently , there are clinical trials aimed at investigating the effectiveness of gemcitabine in combination with other therapeutic agents and our patient is enrolled in such a trial .
choledochal cysts are rare benign growths that can develop into cancerous lesions if left untreated . 
 the cysts are commonly discovered incidentally during imaging procedures for other reasons . 
 surgical resection is recommended to avoid risk of cancer or metastatic disease . 
 a rare case of a non - metastatic cholangiocarcinoma in a longstanding choledochal cyst is presented in this case report .