carcinomas producing granulocyte colony - stimulating factor ( g - csf ) are extremely malignant and have a poor prognosis [ 1 , 2 ] . thus , a liposarcoma producing g - csf is particularly rare and has only been described in a few case reports [ 1 , 3 ] . here , the tumor also showed spontaneous rupture , which has not been previously reported for retroperitoneal liposarcoma . positron emission tomography using f - fluorodeoxyglucose ( f - fdg - pet ) is used to detect tumors based on elevated glucose metabolism in carcinoma cells . it has also been shown that f - fdg uptake by bone marrow is correlated with the peripheral blood neutrophil count , since uptake reflects increased marrow metabolism . we performed f - fdg - pet with computed tomography ( pet / ct ) for imaging of the g - csf - producing tumor and found high f - fdg uptake by the tumor itself and diffuse uptake throughout the bone marrow . these are the first pet / ct images of a g - csf - producing tumor in a urological disease . the patient was a 63-year - old man with a history of hypertension and no specific family history . he was taken to the emergency department of our hospital due to significant aggravation of the pain in late july 2008 . an abdominal ct imaging ( fig . 1 ) revealed a non - fatty , non - fibrotic , and non - calcified right retroperitoneal tumor of 15 cm in size and retroperitoneal hemorrhage . hemorrhagic shock occurred due to spontaneous rupture of the retroperitoneal tumor during the examination , and an emergency transcatheter arterial embolization was conducted . the nutrient vessels were the superior and inferior suprarenal arteries , inferior phrenic artery , renal capsular artery , and the first lumbar artery . three days after admission , the patient was transferred to our department for a more detailed examination of the retroperitoneal tumor . a routine peripheral hematological examination indicated a high white blood cell ( wbc ) count of 37,820/l and a strong left - shift of the differential leukocyte count , with a neutrophil count of 34,794/l . however , no infection appeared to be present based on physiological and biochemical findings , and endocrinological tests showed no abnormal findings . since the wbc count remained high after the transfer to our department , further tests were carried out at the department of hematological internal medicine , based on the suspicion of a g - csf - producing tumor or a comorbid hematological disease . in parallel , elevated uptake of < f - fdg correlated with the tumor site ( maximum standardized uptake value , suvmax , was 18.5 ) and the case was diagnosed as malignant . pet / ct imaging also indicated diffuse uptake throughout the bone marrow , and particularly elevated uptake in the vertebral bone ( suvmax : 10.5 ) ( fig . 2 ) . however , bone scintigraphy showed no bone metastasis , and bone marrow biopsy revealed little fat , significant hyperplasia , and increased neutrophils , but no findings of metastasis or bone marrow involvement . based on all the above findings and the high serum g - csf level of 2,670 pg / ml ( normal < 8 pg / ml ) , the cause of the increased wbc count was determined to be a g - csf - producing tumor . a malignant tumor was suspected and right nephrectomy and retroperitoneal tumorectomy were conducted in mid - september . however , since the tumor had infiltrated into the inferior vena cava , diaphragm and abdominal wall already , only partial resection of the tumor was performed . histopathological tests using hematoxylin - eosin staining showed findings for malignant fibrous histiocytoma mixed with those for well - differentiated liposarcoma ( fig . the tumor was diagnosed as dedifferentiated liposarcoma based on the diagnostic criteria of the world health classification ( who ) [ 5 , 6 ] . the postoperative peripheral wbc count was 21,000/l and the serum g - csf level was 1,170 pg / ml , both of which showed a transient decrease . with informed consent from the patient , only symptomatic therapy , but no chemotherapy or radiotherapy , was carried out while observing the prognosis . liposarcomas are morphologically subdivided into five main subgroups : well - differentiated , myxoid , round cell , pleomorphic , and dedifferentiated . dedifferentiated liposarcoma was first recognized by evans in 1979   and was defined in 2002 as a tumor with a clear - cut and well - differentiated component clearly separated from or occupying a large area beside a poorly differentiated component [ 5 , 6 ] . among 78 cases of retroperitoneal liposarcoma , fabre - guillevin et al .   described 52 cases of dedifferentiated liposarcoma with a differentiated component with features of malignant fibrous histiocytoma ( 36 undifferentiated pleomorphic sarcoma ; 14 fibrosarcoma ; 1 myxofibrosarcoma ; 1 osteosarcoma ; and/or 4 leiomyosarcoma ) , 21 of well - differentiated liposarcoma , 2 of myxoid liposarcoma , 2 of round cell liposarcoma , and 1 of pleomorphic liposarcoma . the cases of dedifferentiated liposarcoma had local recurrence and metastasis at rates of about 40 and 20% , respectively , and a poorer clinical outcome compared to well - differentiated liposarcoma [ 6 , 7 ] . the production of g - csf has been reported in cases of hepatocellular carcinoma , pancreatic cancer , and gastric cancer [ 8 , 9 , 10 ] . g - csf - producing carcinomas show aggressive growth and a very poor prognosis [ 8 , 9 , 10 ] . there have only been a few previous case reports of a g - csf - producing liposarcoma [ 1 , 3 ] . six cases of liposarcoma accompanied by leukocytosis have been described in the english literature . however , the g - csf level has only been evaluated in 3 cases : in an upper arm dedifferentiated liposarcoma described by sakamoto et al . , in a mesenteric pleomorphic liposarcoma reported by nakamura et al . , and in the current case . in all 3 cases , the g - csf level and peripheral wbc counts were correlated with the clinical course . the g - csf level and wbc count showed a transient postoperative decrease in our patient , but this was followed by an aggressive clinical course and the wbc count was 145,800/l at the time the patient died . no hematological diseases such as leukemia or a leukemoid reaction were observed and bone marrow biopsy only showed hyperplasia . these findings led to the diagnosis of a g - csf - producing retroperitoneal dedifferentiated liposarcoma . this is an extremely rare clinical presentation , with the description of spontaneous rupture of a renal liposarcoma by mazuch et al . the rapid aggressive growth of the g - csf - producing tumor may have caused the rupture , and palliative surgery was performed because of the rupture . pet / ct is useful for the evaluation of malignant lesions . in cases of carcinoma , diffuse f - fdg uptake in bone marrow is often indicative of bone metastasis or bone marrow involvement . in our case , pet / ct showed diffuse f - fdg uptake throughout the bone marrow , which indicated multiple bone metastases . described 2 cases of g - csf - producing lung cancer that showed diffuse f - fdg uptake throughout the bone marrow . commented that diffuse elevated f - fdg uptake in bone marrow may be helpful in the diagnosis of a g - csf - producing tumor . bone metastasis is a differential diagnosis , and in our case bone scintigraphy and bone marrow biopsy were useful for ruling out bone metastasis . murata et al .   showed that f - fdg uptake by bone marrow is strongly correlated with the wbc count ( especially neutrophil count ) and suggested that f - fdg uptake by bone marrow reflects marrow metabolism , which is mainly regulated by granulocyte progenitors and stimulated by endogenous hematopoietic growth factors . found increased f - fdg uptake in patients treated with g - csf and showed that the increased uptake returned to the pretreatment value approximately 1 month after discontinuation of g - csf . the serum g - csf level is likely to be higher in patients with a g - csf - producing tumor than in those treated with g - csf thus , for a g - csf - producing tumor , at least 1 month is needed before a pet / ct evaluation after removal of the primary lesion . other conditions associated with diffuse f - fdg uptake in the bone marrow include marrow hyperplasia resulting from hemolytic / iron - deficiency / blood - loss anemia . in addition , van de weile et al .   examined the relationship between bone marrow f - fdg uptake and levels of serum cytokines . in patients with non - small cell lung carcinomas , which are known to produce cytokines , f - fdg uptake by bone marrow thus , bone marrow f - fdg uptake in patients with a g - csf - producing tumor may also be related to cytokines such as tgf-. in conclusion , we encountered a rare case of a g - csf - producing retroperitoneal dedifferentiated liposarcoma that underwent spontaneous rupture due to rapid aggressive growth . this case is also the first report of pet / ct imaging of a g - csf - producing tumor in a urological disease . in such cases , one needs to be careful to avoid a misdiagnosis of bone metastasis , but imaging may be useful for differential diagnosis of a g - csf - producing tumor in patients with abnormally high wbc counts in the absence of infection .
the patient was a 63-year - old man who was referred to our hospital as an emergency case with the chief complaint of abdominal pain . 
 an abdominal ct revealed a right retroperitoneal tumor of 15 cm and retroperitoneal bleeding . 
 after a transcatheter arterial embolization was performed , the patient was transferred to our department . 
 there was no infective focus . 
 the white blood cell ( wbc ) count ( 37,820/l , normal range < 8 pg / ml ) and the serum granulocyte colony - stimulating factor ( g - csf ) level ( 2,670 pg / ml , normal range < 8 pg / ml ) were high . 
 bone marrow biopsy revealed little fat , significant hyperplasia , and predominantly increased neutrophils , but no findings of bone metastasis or bone marrow involvement . 
 a g - csf - producing tumor was diagnosed and right nephrectomy and retroperitoneal tumorectomy were performed . 
 however , the tumor had infiltrated into the inferior vena cava , diaphragm and abdominal wall , and only part of the tumor could be removed . in histopathological tests , 
 hematoxylin - eosin staining showed malignant fibrous histiocytoma - like findings mixed with those for well - differentiated liposarcoma , and the case was diagnosed as dedifferentiated liposarcoma . 
 preoperative 18f - fdg - pet computed tomography showed diffuse 18f - fdg uptake throughout the bone marrow and elevated uptake at the tumor site . 
 however , since bone biopsy and bone scintigraphy indicated no bone metastasis or bone marrow involvement , we concluded that pet / ct imaging gave false - positive results in the bone marrow . 
 this is the first report of pet / ct imaging of a g - csf - producing tumor in a urological disease . 
 the imaging results may be useful for differential diagnosis for this tumor in patients with high wbc counts without infection .