granulocytic sarcoma ( gs ) is a localized tumor composed of immature myeloid cells in extramedullary sites . it usually presents concomitantly with or after the onset of acute myelogenous leukemia ( aml ) , blastic phase of chronic myelogenous leukemia or myelodysplastic syndrome ( 1 - 3 ) . on rare occasions , gs may present as nonleukemic gs . by definition , nonleukemic gs occurs without present overt leukemia , and in the absence of any past history of aml , myelodysplasia , or myeloproliferative disorders ( 2 - 4 ) . nonleukemic gs may involve any part of the body , and the most common sites of involvement are skin , subcutaneous tissue , lymph nodes , central nervous system , gastrointestinal tract , mediastinum , bone , breast , ovary and uterus ( 2,3,5 ) . although nonleukemic gs may be found in any location , primary occurrence in the bile duct is extremely rare . in this report , we describe an extremely rare case of a nonleukemic gs of the bile duct , which was initially misdiagnosed as a bile duct carcinoma arising in the hilum of the liver ( so - called klatskin tumor ) . the complete blood count showed hemoglobin of 15 g / dl , white blood cell count of 8,200/l ( differential 79% segmented neutrophils , 15% lymphocytes , 5% monocytes , and 1% eosinophils ) , and platelet count of 248,000/l . liver function test showed elevation of total bilirubin , direct bilirubin , and alkaline phosphatase ( 15.3 mg / dl , 9.4 mg / dl and 298 iu / l , respectively ) . computed tomography of the abdomen revealed thickening of common bile duct wall , luminal narrowing at common hepatic duct level and mild , diffuse dilatation of intrahepatic duct ( fig . magnetic resonance cholangiography showed dilatation of both intrahepatic duct and right posterior duct ( fig . 2 ) . based on these findings , a common hepatic duct cancer ( klatskin tumor ) histological examination of the tumor showed diffuse thickening of the common bile duct wall with encroachment of the lumen and obliteration of the mucosal folds by the dense cellular infiltrate . the great majority of the cells in the infiltrate consisted of myeloid precursors with large round to oval cells with slightly eosinophilic cytoplasm and round to oval vesicular nuclei , admixed with a minor population of more mature myeloid forms including eosinophils ( fig . immunohistochemical stains showed tumor cells positive for leukocyte common antigen ( cd 45 ) and myeloperoxidase ( fig . 4 ) , and negative for cd 3 , 4 , 5 , 8 , 10 , 21 , 23 , 56 and terminal deoxynucleotidyl transferase . bone marrow aspirate and biopsy showed neither significant abnormalities nor evidence of myelodysplasia or leukemic infiltration . considering the risk of subsequent development of overt leukemia ( 3 ) , the patient received antileukemic induction chemotherapy consisting of cytarabine 200 mg / m / day ( days 1 - 5 ) and daunorubicin 45 mg / m / day ( days 1 - 3 ) , and a course of consolidation with high dose cytarabine ( cytarabine 6 g / m / day , days 1 , 3 , 5 ) subsequently . to date , he has remained free of disease for 15 months . although nonleukemic gs may involve any part of the body , nonleukemic gs of the bile duct is extremely rare . to the best of our knowledge , there have been only 1 case report of nonleukemic gs of the bile duct in the medical literatures . ( 6 ) reported a patient who present with obstructive jaundice and underwent endoscopic retrograde biliary drainage . he developed acute aml within 1 month . a frequent problem reported with nonleukemic gs is initial misdiagnosis . correct initial diagnosis of nonleukemic gs is very important because misdiagnosis could lead to inappropriate treatment and hence , to the risk of missing a chance for cure . however , due to its rarity , nonleukemic gs is frequently misdiagnosed as other common malignancies , as was the case with our patient being initially misdiagnosed as a bile duct carcinoma . even after the histologic examination , gs may be misdiagnosed as other malignancies , most often as lymphoma ( 2,3 ) . because considerable cases of gs do not show morphologic evidence of granulocytic differentiation , could exhibit features mimicking lymphoma and may co - express myeloid and lymphoid markers , histologic diagnosis of gs can be difficult if it is not suspected ( 1,7 ) . in one case series , 75% of the cases with nonleukemic gs were initially misdiagnosed , 50% as lymphoma , and 25% as nonhematopoietic neoplasm ( 2 ) . in another case series , 35 ( 47% ) of 74 patients with nonleukemic gs were initially misdiagnosed ( 5 ) . among them , 31 patients were mistaken for lymphoproliferative disorders . the correct diagnoses were usually made when the lesion recurred or after overt leukemia developed thereafter ( 2,5 ) . thus , for correct initial diagnosis and adequate therapy , it is important to suspect the possibility of nonleukemic gs and to apply appropriate immunohistochemical staining for differential diagnosis . nonleukemic gs represents therapeutic dilemma as well as a diagnostic one because the optimal therapy for nonleukemic gs has not been determined . several previous reports showed that more than 80% of patients with nonleukemic gs who were treated by surgical excision or local radiation therapy eventually developed overt systemic leukemia within a matter of months ( 1,3,8,9 ) , which suggests that local treatments such as surgical excision or radiation therapy would not be sufficient for the treatment of nonleukemic gs . for this , the importance of systemic chemotherapy as used for aml early in the course of the disease was advocated by several retrospective studies ( 2,5,10 ) . ( 2 ) found that in the 19 patients who received surgical or radiation therapy for nonleukemic gs eventually developed aml . in contrast , only 5 ( 42% ) of 11 patients treated with systemic chemotherapy developed rospective review of 90 nonleukemic gs cases , patients treated with systemic chemotherapy had a decreased probability of developing aml and experienced longer overall survival . in all , 59 ( 66% ) of the 90 patients developed aml at a median 9 months after the diagnosis of nonleukemic gs and the median overall survival was 22 months . a total of 49 ( 54% ) of 90 patients received chemotherapy and were less likely to develop aml as compared with those who did not receive chemotherapy ( 41% vs. 71% , p=0.001 ) . in addition , leukemia occurred significantly later in those patients who received systemic chemotherapy . the median time from diagnosis of nonleukemic gs to leukemia was 36 months in patients treated with chemotherapy compared with 6 months in untreated patients . most importantly , the overall survival was longer in the patients who received chemotherapy than in the patients who did not ( more than 50% alive after a median follow up of 25 months compared with a median survival of 13 months in those who did not receive chemotherapy ) . of note is that multivariate analysis revealed that neither radiation nor surgery alone had any effect on survival . these patients were divided into 3 groups by therapeutic regimens ; group i included 12 patients who received only biopsy or surgical resection of the tumor , group ii was 20 patients who received local radiation , and group iii consisted of 42 patients who received systemic chemotherapy . the nonleukemic period after the diagnosis of gs was significantly longer in group iii than in the other groups ( median , 12 months in group iii vs. 3 and 6 months in group i and ii , respectively ) . according to the findings of the above studies , it appeared that patients with nonleukemic gs should receive aml type systemic chemotherapy at the time of diagnosis , and surgery and/or radiation therapy alone would be insufficient treatment of nonleukemic gs . in the present case , considering the risk of subsequent development of overt leukemia , we treated the patient with two cycles of aml type combination chemotherapy and he has remained free of disease 15 months after treatment . a few patients with nonleukemic gs also underwent allogeneic or autologous bone marrow transplantation ( 10 ) however , the efficacy of allogeneic or autologous bone marrow transplantation in the therapy of nonleukemic gs has not been defined . in conclusion , nonleukemic gs is frequently misdiagnosed as other more common malignancies because of its rarity and clinico - pathological features mimicking other malignancies . with a high index of suspicion , the application of immunohistochemical techniques enables the differential diagnosis from aggressive lymphoma that represents the commonest misdiagnosis . considering the poor outcome after local treatment for nonleukemic gs , the patients with nonleukemic gs should be treated with intensive aml type systemic chemotherapy early in the course of the disease .
granulocytic sarcoma ( gs ) is an extramedullary tumor composed of immature myeloid cells , typically occurring during the course of acute myelogenous leukemia . 
 nonleukemic gs , that is , gs with no evidence of overt leukemia and no previous history of leukemia , is very rare , and even more unusual is nonleukemic gs of the bile duct . 
 we report a case of nonleukemic gs of the bile duct . 
 the patient was initially misdiagnosed as a bile duct carcinoma arising in the hilum of the liver ( so - called klatskin tumor ) , and received a right lobectomy of the liver . 
 histological examination of the tumor yielded the diagnosis of gs , and the bone marrow biopsy did not show any evidence of leukemia . considering the risk of subsequent development of overt leukemia , the patient was treated with two cycles of combination chemotherapy as used in the cases of acute myelogenous leukemia . to date , he has remained free of disease 15 months after treatment .