inflammatory myofibroblastic tumor ( imt ) is rare and characterized by spindle cell proliferation with inflammatory cell infiltration .
because of its cytological features and infiltrative nature , it may be difficult to distinguish histologically from malignant sarcomatous lesions .
a 36-year - old male was referred to our hospital for further examination of a bladder tumor .
cystoscopy revealed a broad - based tumor 40 mm in diameter ( fig 1 ) .
he had a medical history of hyperlipidemia , diabetes mellitus , asthma , and bipolar disorder .
the hematological and biochemical data showed no abnormal findings without elevation of hba1c of 8.4% .
the tumor markers were also within normal limits ( cea 1.4 ng / ml , ca125 12 u / ml , ca199 7 u / ml ) . magnetic resonance imaging ( mri ) showed a 40  25-mm mosaic bladder mass of high intensity on diffusion images ; the tumor was suspected to have invaded the muscle ( fig 2 ) , but computed tomography revealed no distant metastasis .
histologically , the urothelium showed no atypia . in the submucosa , spindle cells proliferated in interlacing fascicles or storiform arrays with inflammatory cell infiltration .
immunohistochemically , the spindle tumor cells were strongly positive for anaplastic lymphoma kinase ( alk ) and smooth - muscle actin , weakly positive for cytokeratin ae1/ae3 and p53 but negative for desmin . based on these findings , the tumor was diagnosed as imt .
the patient has not experienced recurrence in the 10 months since resection of the bladder tumor .
the hematological and biochemical data showed no abnormal findings without elevation of hba1c of 8.4% .
the tumor markers were also within normal limits ( cea 1.4 ng / ml , ca125 12 u / ml , ca199 7 u / ml ) . magnetic resonance imaging ( mri ) showed a 40  25-mm mosaic bladder mass of high intensity on diffusion images ; the tumor was suspected to have invaded the muscle ( fig 2 ) , but computed tomography revealed no distant metastasis .
histologically , the urothelium showed no atypia . in the submucosa , spindle cells proliferated in interlacing fascicles or storiform arrays with inflammatory cell infiltration .
immunohistochemically , the spindle tumor cells were strongly positive for anaplastic lymphoma kinase ( alk ) and smooth - muscle actin , weakly positive for cytokeratin ae1/ae3 and p53 but negative for desmin . based on these findings , the tumor was diagnosed as imt .
no adverse perioperative events were observed . the patient has not experienced recurrence in the 10 months since resection of the bladder tumor .
imt  also known as postoperative spindle cell nodule , pseudosarcomatous fibromyxomatous tumor , and reactive pseudosarcomatous response  involve only inflammatory cells .
these tumors have been observed in any organ , including the lung , liver , and kidney .
the most frequently reported symptom is gross hematuria followed by urinary pain , dysuria , and increased urination frequency .
the tumor has been observed in a wide range of ages , from around 30 to 50 years , with an equal balance of genders .
although the causes of this tumor have long been believed to be urinary tract infection , surgical invasion , diabetes mellitus , and immune disorders , a number of idiopathic cases have also been reported [ 4 , 5 ] . in our case ,
the patient had diabetes mellitus . in this case , the tumor size was around 4 cm in diameter .
reported imts were around 25 cm in most cases , but 1 case showed 37.5 cm [ 1 , 4 ] . due to the risk of local recurrence , complete resection is recommended . on the other hand ,
grossly , imt shows a variety of forms , but in most cases , the tumor adopts a nonpapillary form with a rounded surface . on mri ,
the tumor typically shows low intensity on t1-weighted imaging and high intensity at the surface with low intensity inside on t2-weighted imaging .
histologically , imt is characterized by proliferation of myofibroblastic spindle cells and inflammatory cell infiltration .
the most important entities in differential diagnosis are sarcomatoid urothelial carcinoma , leiomyosarcoma , and rhabdomyosarcoma because of the similarity of histological findings . finding cytological atypia and atypical mitotic figures and immunostaining with alk are useful to differentiate imt from other malignant spindle cell tumors [ 1 , 9 ] .
although there have been no reports of distant metastasis , intravesicle recurrence was reported after transurethral resection .
partial bladder resection is required after transurethral resection . however , in cases of benign tumors , total cystectomy should not be performed due to the risk of misdiagnosing them as sarcomatoid carcinoma .
 a 36-year - old male was referred to our department for further examination of asymptomatic gross hematuria emanating from a bladder tumor . 
 cystoscopy revealed a broad - based tumor 40 mm in diameter . 
 urinary cytology was negative . 
 preoperative magnetic resonance imaging suggested a muscle invasive tumor . 
 transurethral resection was performed , and the pathological findings revealed an inflammatory myofibroblastic tumor . 
 we herein report a rare case of bladder inflammatory myofibroblastic tumor . 
Introduction
Case Presentation
Laboratory Data and Imaging Findings at the Time of Admission
Operative Procedure and Pathological Findings
Postoperative Course
Discussion
Statement of Ethics
Disclosure Statement