malignant extrahepatic bile duct obstruction is mostly caused by primary bile duct cancer , or via the metastasis of other tumors to the peripancreatic , periportal , peribiliary lymph nodes , and the head of the pancreas.1 the primary cancers that cause metastatic biliary obstruction include carcinomas from the stomach , colon , lung , uterus , and breast . among them , common malignant tumors that could cause metastatic extrahepatic bile duct obstruction are stomach cancer and colon cancer;23 however , biliary obstruction associated with metastatic mucinous adenocarcinoma of the colon to the distal common bile duct is even rarer in non - biliary cancers . moreover , colonic mucinous adenocarcinoma is relatively rare , accounting for less than 5% of colorectal cancers ; when it is diagnosed at an advanced stage , the prognosis is worse.4 in the literature review , there is no report regarding metastatic mucinous adenocarcinoma of the distal common bile duct from colon cancer- thus , we present a sample case of this disease . a 70-year - old man presented with obstructive jaundice and weight loss , for two weeks . he did not have a history of hypertension , diabetes mellitus , tuberculosis and liver disease . upon a physical examination , the patient did not appear to be so ill - looking , and showed icteric sclera . a laboratory evaluation revealed obstructive jaundice with a total bilirubin of 5.4 mg / dl , alkaline phosphatase of 640 iu / l , aspartate aminotransferase of 573 iu / l , and alanine aminotransferase of 841 iu / l . the carcinoembryonic antigen ( cea ) was 2.4 ng / ml , the alpha - fetoprotein was 3.05 ng / ml , and the carbohydrate antigen 19 - 9 ( ca19 - 9 ) was 61 u / ml . abdominal computed tomography ( ct ) scan , and abdominal magnetic resonance imaging detected a 2.5 cm - sized enhancing soft tissue lesion at the distal common bile duct , with involvement of the cystic duct and gallbladder neck , thus narrowing the common hepatic duct and dilating the proximal duct , by which bile duct cancer was suspected ( fig . , they showed eccentric enhancing wall thickening in the proximal transverse colon , which is suggestive of concomitant colon cancer ( fig . 2 ) . colonoscopy revealed a lumen - encircling ulcerofungating mass in the proximal transverse colon that was pathologically proven to be adenocarcinoma . endoscopic retrograde cholangiopancreatography ( ercp ) was performed to relieve obstructive jaundice , and to confirm the tissue pathology of the bile duct lesion as well . pylorus - preserving pancreaticoduodenectomy and extended right hemicolectomy were performed under the diagnosis of double primary cancers , at the common hepatic bile duct and transverse colon ( fig . 3 ) . a postoperative histopathologic examination revealed a moderately differentiated mucinous adenocarcinoma of the transverse colon cancer ( pt4an2b ; 14 out of 35 lymph nodes ) and a mucinous adenocarcinoma of the distal common bile duct ( pt2n1 ; 2 out of 4 lymph nodes ) . immunohistochemical staining studies showed cytokeratin 7 ( - ) , cytokeratin 19 ( + ) , cytokeratin 20 ( + ) , cdx2 ( + ) , and p53 ( - ) , by which we concluded that the bile duct cancer had metastasized from colon cancer ( fig . the patient recovered uneventfully from surgery , and will be undergoing adjuvant systemic chemotherapy for three months . patients with primary bile duct cancers typically present with painless jaundice resulting from the perihilar or distal biliary strictures , or with an intrahepatic mass , causing abdominal pain . common non - biliary malignancies that can cause distal biliary obstruction are : stomach cancer , colon cancer and breast cancer;2 however , biliary obstruction caused by mucinous adenocarcinoma of the colon is rare , and is mostly due to the compression of the bile duct by metastasis to the surrounding the lymph nodes , or to the pancreas head . the most frequent site of metastatic malignant biliary obstruction is the common bile duct , at the level of the cystic duct.5 in general , metastatic lymphadenopathy in the hepatoduodenal ligament is the main cause of biliary obstruction.6 according to some reports , however , the hepatic hilum was the most common level of obstruction.78 moon et al . reported that the proximal common bile duct ( 20/50 , 40% ) and hilum ( 18/50 , 36% ) were the most frequent levels of biliary obstruction , followed by the periampullary area ( 14% ) and the distal common bile duct ( 10% ) , because of biliary obstruction in metastatic cancer.2 in this case , the abdominal ct showed a 2.5 cm - sized enhancing soft tissue lesion in the distal common bile duct , causing a biliary obstruction . even though the status of the primary extra - biliary malignant disease can affect the therapeutic strategy for double primary intraductal cholangiocarcinoma , radical surgical resection is still an option if the primary extra - biliary malignancy is well controlled.3 there is no concrete evidence , however , that the surgical resection of metastatic lesions ( including intraductal lesions ) increases patient survival unless the patient has hepatic metastasis resulting from colorectal cancer . in our case , pylorus - preserving pancreatoduodenectomy , with extended right hemicolectomy , was performed under the diagnosis of double primary cancers of the common hepatic bile duct and transverse colon . in preoperative imaging evaluation , there was no evidence of metastasis originating from the double primary cancers . when an intraductal lesion was detected on the ct images of a patient with extra - biliary neoplasm , the following findings were found to be suggestive of intraductal metastasis , rather than intraductal cholangiocarcinoma : colorectal cancer as the extra - biliary malignant disease , a parenchymal mass that was contiguous with the intraductal lesion , and expansile growth of the intraductal lesion.3 the significant point that differentiates intraductal metastasis from intraductal cholangiocarcinoma was the morphologic features of the intraductal lesion . the appearance of the intraductal lesion in pathologic specimens differed for intraductal metastasis and intraductal cholangiocarcinoma , which contributed to the differences in the diagnostic imaging features.9 in the intraluminal extension , the tumor grows in the ductal lumen as papillary projections , resembling tumor thrombi . however , in the intraepithelial extension , the cancer cells advance along the intact basement membranes and replace the non - neoplastic biliary ductal epithelium . usually , intraductal metastasis exhibits expansile intraluminal extension , but intraductal cholangiocarcinoma exhibits intraepithelial extension with a papillary growth pattern , due to its origination from the underlying papilloma or adenoma.10 we performed immunohistochemical staining studies , as an additional tool for the differentiation of intraductal metastasis and intraductal cholangiocarcinoma . the immunohistochemical reaction to cytokeratin , such as cytokeratin 7 and cytokeratin 20 , is well known to enhance the diagnosis.9 the colorectal epithelium is immunoreactive to the anticytokeratin 20 antibody , but not to anticytokeratin 7 antibody , which is reactive to biliary epithelium . therefore , a cytokeratin 20-positive and cytokeratin 7-negative immunohistochemical staining pattern is a characteristic of biliary metastasis from colorectal cancer.11 cytokeratin 19 is normally expressed in the lining of the gastropancreatic and hepatobiliary tracts , which is positive in most adenocarcinomas in the gastrointestinal tract and pancreas.12 the expression of cdx2 in adults is restricted to the intestine , from the duodenum to the rectum . cdx2 is regarded as a specific marker of the intestinal epithelial cells , that can be utilized for identifying the colorectal origin of metastatic adenocarcinomas.13 p53 is a tumor suppressor gene that is located on the short arm of chromosome 17 , and the p53 mutation is required for the development of colorectal cancer , and is associated with an increased relative risk of death , and poorer prognosis.114 in conclusion , we should take metastatic lesions into consideration , when an intraductal lesion is found in a patient with colorectal malignancy , or a history of colorectal cancer . to our knowledge , this is the first report regarding metastatic mucinous adenocarcinoma of the distal common bile duct , resulting from colon cancer .
the patient was a 70-year - old male whose chief complaints were obstructive jaundice and weight loss . 
 abdominal imaging studies showed a 2.5 cm sized mass at the distal common bile duct , which was suggestive of bile duct cancer . 
 eccentric enhancing wall thickening in the transverse colon was also shown , suggesting concomitant colon cancer . 
 a colonoscopy revealed a lumen - encircling ulcerofungating mass in the transverse colon , that was pathologically proven to be adenocarcinoma . 
 the bile duct pathology was also adenocarcinoma . 
 pylorus - preserving pancreaticoduodenectomy and extended right hemicolectomy were performed under the diagnosis of double primary cancers . 
 postoperative histopathologic examination revealed moderately differentiated mucinous adenocarcinoma of transverse colon cancer , and mucinous adenocarcinoma of the distal common bile duct . 
 immunohistochemical staining studies showed that the bile duct cancer had metastasized from the colon cancer . 
 the patient recovered uneventfully from surgery and will be undergoing chemotherapy for three months .