adenomas of the colon and rectum are very common benign neoplasms , but adenomas of the common bile duct ( cbd ) are very rare diseases ( 1,2 ) . since bile duct adenomas often cause obstructive jaundice , patients are suspected to have cbd stones or malignant neoplasms . adenomas of the bile duct are essentially benign tumors , although they are occasionally considered to be premalignant tumors . intraductal papillary neoplasms of the bile duct ( ipnb ) have been proposed to be the biliary counterpart of intraductal papillary mucinous neoplasms of the pancreas , and the processes of the adenoma - to - carcinoma sequence in bile duct neoplasms have been identified ( 35 ) . treatments for bile duct adenoma are necessarily based on diagnostic results , and local resections of the cbd may be performed if the distal and proximal cut ends are free from the tumor , and the tumor is diagnosed to be benign . when a bile duct resection is insufficient for complete resection , or if a malignant transformation of the tumor is suspected , consequently , pancreatoduodenectomy should be considered ( 5 ) . fluorine-18 fluorodeoxyglucose positron emission tomography ( f - fdg pet ) is used for cancer diagnosis and staging , and is often used for cbd tumors . f - fdg pet is known to have 92.3% sensitivity , and 92.9% specificity , in the diagnosis of bile duct cancer ( 6 ) , although whether f - fdg pet is able to differentially discriminate between diagnoses of adenoma and carcinoma of the bile duct remains to be fully elucidated . in the present study , a case of bile duct adenoma with low - grade atypia was reported , demonstrating the uptake of f - fdg , which was successfully treated by surgical resection . he had diabetes mellitus and hypertension , which were controlled by the use of oral medicines . a physical examination revealed normal findings in the patient 's abdomen . laboratory analyses , however , revealed increased levels of total bilirubin ( 40.4 mol / l ) , direct bilirubin ( 21.0 mol / l ) , alkaline phosphatase ( 507 units / l ) , -glutamyl transpeptidase ( 364 units / l ) , aspartate aminotransferase ( 1,578 units / l ) and alanine aminotransferase ( 1,132 units / l ) . tumor markers , including carcinoembryonic antigen and carbohydrate antigen 19 - 9 , were shown to be within the normal range . computerized tomography ( ct ) revealed a slight dilation of the cbd , with the identification of a mass in the distal cbd ( fig . following a diagnosis of obstructive jaundice , endoscopic nasobiliary drainage was performed after the admission of the patient . radiological examinations revealed the presence of a 25 mm fixed filling defect in the distal cbd , and intraductal ultrasonography revealed an isoechoic , and partially high echoic , mass ( figs . a biopsy of this lesion revealed the presence of tubular adenoma with low - grade atypia . f - fdg pet demonstrated an accumulation of focal increased tracer in this lesion , with a maximum standard uptake value ( suvmax ) of 3.3 , and the position where uptake of the f - fdg occurred was separate from the drainage tube ( fig . on the basis of these findings , a pylorus - preserving pancreatoduodenectomy and regional lymph - node dissection were performed . the tumor was impacted in the bile duct lumen , occupying 2.5 cm in length ( fig . histological examinations revealed that the tumor was composed of relatively uniform tubules , with a bland cellular appearance . furthermore , invasion was not observed in the duct wall , and no intraductal mass was identified ( fig . a grade b pancreatic fistula was identified following the surgery , although the patient was discharged 40 days post - surgery . the patient remains alive , with no evidence of any recurrence of the tumor , 15 months following the surgery . benign tumors arising from the extrahepatic biliary tree are very rare , and are reported to occupy 6% of all tumors of the bile ducts ( 2 ) . in benign tumors , adenomas and papillomas are commonly encountered . adenomas arise from the epithelial lining of the biliary duct , and grow in a tubular , papillary or a tubulopapillary manner . the adenoma - to - carcinoma sequence has been well established to occur in the colon and the rectum , and this also applies in the ampullary region ( 710 ) . in carcinoma of the ampulla of vater , adenomatous areas were revealed to co - exist with high frequency in > 40% of the surgically resected specimens ( 11,12 ) . previously , ipnb have been proposed to be the biliary counterpart of intraductal papillary mucinous neoplasms of the pancreas ( 3,4 ) . ipnb are a major intraductal neoplasm , which is capable of progressing to an invasive carcinoma , and the types of cytoarchitectural atypia in ipnb were characterized as adenoma , borderline , carcinoma in situ and invasive carcinoma ( 3 ) . the development of ipnb was reported to follow an adenoma - to - carcinoma sequence , which correlated with the stepwise activation of common oncogenic pathways , including mutated kirsten rat sarcoma viral oncogene homolog , the overexpression of tumor protein 53 and loss of p16 ( 13 ) . kim et al ( 1 ) summarized the 26 cases of adenomas arising from cbd , and reported that the histological findings ranged from adenoma without atypia to carcinoma in situ with an adenoma component . therefore , complete resection of the lesion is required in order to avoid the postoperative development of bile duct carcinoma . endoscopic resection for bile duct adenoma has been infrequently reported , and the technique is considered to be applicable only in a limited number of situations , for example , for patients for whom surgical resection would pose a high risk ( 14,15 ) . local resection of the cbd may be performed if the distal and proximal cut ends are free from the tumor and the tumor is diagnosed to be benign . if the extent of the bile duct adenoma occupies a range which reaches to the distal cbd and local resection is impossible , pancreatoduodenectomy should be considered for complete resection . in adenoma of the bile duct , kim et al ( 1 ) reported that radical resection may be required in cases where the size of the adenoma was > ~20 mm , or where malignant transformation was suspected . in the present case study , the tumor was located in the distal bile duct in the pancreas , and consequently , pancreaticoduodectomy was selected as the procedure , not bile duct resection . based on the results obtained from the f - fdg pet , the regional lymph node was also dissected . had the results of the f - fdg pet proven to be negative , lymph node dissection would not have been necessary . f - fdg pet has been applied in clinical practice to detect a wide variety of tumor types , including lymphoma , lung , esophageal , colon and bile duct cancer ( 1619 ) . for patients with extrahepatic cholangiocarcinoma , f - fdg pet furthermore , choi ek et al ( 21 ) reported that the suvmax value identified from pet - ct scans is a useful parameter to enable the differentiation of an extrahepatic biliary malignancy from benign disease . in the meta - analysis , annunziata et al ( 22 ) reported that the sensitivity and specificity of f - fdg pet were 76 and 74% , respectively , for extrahepatic cholangiocarcinoma . several previous studies reported that false - negative results obtained in cases of f - fdg pet were due to the morphology of extrahepatic cholangiocarcinoma ( 20,23 ) . infiltrative types of cholangiocarcinoma led to discrepancies in the diagnostic performance due to an insufficient uptake of fdg in the tumor . however , an explanation of how an uptake of fdg was observed with benign biliary tumors was not forthcoming , and neither was it discussed . f - fdg pet detects premalignant colonic adenomas , and a focal fdg accumulation is detected in > 50% of reported cases ( 24 ) . the degree of fdg uptake was reported to be correlated with the size of the adenoma , or to the degree of dysplasia ( 25 ) . for results obtained from f - fdg - pet of the bile duct adenoma , dong et al ( 26 ) reported two cases of ipnb , with uptake of fdg , in 2012 . histological findings revealed that these cases were adenomas , with a high - grade dysplasia in one case , and a low - grade dysplasia in the other . the authors reported that the reason for an uptake of fdg in the adenoma was , primarily , high - mitotic activity across the entire range , from low - grade to high - grade dysplasia , and , secondly , the larger tumor size , composed of a greater number of tumor cells ( 26 ) . in the present case study , the adenoma was 25 mm in diameter with low - grade atypia , and it was hypothesized that the tumor size of the adenoma and the histological grade of atypia correlated with the extent of fdg accumulation . false - positive results obtained with fdg uptake which are due to inflammatory causes are well recognized . wakabayashi et al ( 27 ) reported that , in diagnosing malignant diseases in patients with biliary stricture , fdg - pet was superior as a method compared with ct examination in terms of both the sensitivity and the specificity , and superior to cytological examination of the bile in terms of its sensitivity . anderson et al ( 28 ) described a false - positive result in a patient scanned following a cholecystectomy , with fdg uptake identified during the analysis of residual post - operative inflammatory changes . in the present case study , the bile duct drainage tube for obstructive jaundice was already inserted at the time of pet scan . in a previous report , choi et al ( 21 ) evaluated the clinical value of f - fdg pet for differentiating extrahepatic cholangiocarcinoma from benign disease . in that study , the final diagnosis was of cholangiocarcinoma in 34 patients , and of benign disease in five other patients . of all 39 patients studied , 20 of them had either an endoscopic or external biliary drainage tube , or a biliary stent , at the time of the pet scan . only one patient was false - positive , with a hyperplastic polyp in the ampulla of vater , and the update of fdg was correlated with the drainage tube . in the present case study , the site of fdg uptake was observed to be separate from that of the drainage tube . in addition , kitamura et al ( 18 ) examined the prognostic value of f - fdg pet in extrahepatic bile duct cancers . the authors reported that no significant correlation was identified between fdg uptake and the presence of a biliary drainage tube , or the levels of c - reactive protein . therefore , it was not possible to conclude that the presence of the biliary drainage tube did not affect the measurement of fdg uptake . in conclusion , a case of bile duct adenoma with low - grade atypia showing fdg uptake has been reported in the present study . f - fdg pet may be used to detect premalignant tumors of the bile duct , although whether f - fdg pet is able to differentially discriminate between diagnoses of adenoma and carcinoma of the bile duct remains to be fully elucidated , and the assessment of further case studies is required .
a 64-year - old man presented with epigastric discomfort and nausea . 
 laboratory analyses revealed increased levels of total and direct bilirubin , and increased levels of aminotransferases . 
 computed tomography revealed the presence of a mass in the distal common bile duct . 
 endoscopic retrograde cholangiopancreatography and intraductal ultrasonography revealed a 25 mm filling defect in the distal common bile duct , and biopsy of the lesion disclosed the presence of tubular adenoma . using fluorine-18 fluorodeoxyglucose positron emission tomography ( 18f - fdg pet ) revealed an increased accumulation of the tracer in the lesion , with a maximum standard uptake value ( suvmax ) of 3.3 . 
 the patient received a pylorus - preserving pancreatoduodenectomy . 
 the histopathological examination revealed a tubular adenoma with low - grade atypia . 
 the patient remains alive 15 months following the surgery , with no evidence of recurrence of the adenoma . 
 18f - fdg pet has been successfully applied in clinical practice to detect a wide variety of tumor types , including lymphoma , lung , colon and bile duct cancer . in the present study , 
 a case of bile duct adenoma with low - grade atypia was reported , revealing the uptake of 18f - fdg . 
 18f - fdg pet may be able to detect premalignant tumors of the bile duct , although whether 18f - fdg pet is able to differentially discriminate between diagnoses of adenoma and carcinoma of the bile duct remains to be fully elucidated , and the assessment of further case studies is required .