synovial sarcoma ( ss ) most commonly affects the para - articular regions of the extremities of young adults , .
occasionally , however , ss has been identified in less common locations , including the head and neck , heart , lungs and prostate .
herein , we describe a case of primary renal ss , an exceedingly rare diagnosis , in a 52-year - old woman .
the diagnosis was established by histology and immunostaining . to our knowledge , based on a review of the english literature , this marks the first case report describing the magnetic resonance ( mr ) features of synovial sarcoma of the kidney .
a 52-year - old female presenting with a history of right flank pain underwent computed tomography ( ct ) examination which revealed an amorphous partially cystic right lower pole renal mass with heterogeneous enhancement . further workup with
magnetic resonance imaging revealed a 6.0    5.9    6.1  cm mass in the lower pole of the right kidney .
three - plane localizer , coronal single shot fast spin echo ( ssfse ) t2 , axial in and out of phase , axial fat suppressed t2 weighted , axial 5-min and 10-min delayed , and axial 3d liver acquisition with volume acceleration ( lava ) sequences were acquired . on t1 weighted imaging ( fig .
1a ) , the mass was heterogeneous , with the posterior region having similar intensity to skeletal muscle and the anterior region with higher signal intensity .
axial t2 weighted imaging revealed marked heterogeneity with areas of high , intermediate , and low signal , known as the  triple sign ( fig . 1b ) .
the mass contained multiple areas of high t2 signal emanating from the center of the mass , with surrounding intermediate and low t2 signal intensity regions ( fig .
figure 1axial in - phase t1 weighted gradient recalled echo ( gre ) image ( a ) , showing a heterogeneous mass lesion involving the medial portion of the lower pole of the right kidney ( arrow ) , with a posterior isointense area and an anterior area of higher signal intensity , relative to skeletal muscle .
axial fat suppressed t2 ( b ) and coronal ssfse t2 images ( e ) show marked heterogeneity and the 
triple sign ; : areas of low , intermediate and high signal intensity ( arrows ) .
axial post - contrast gre image ( c and d ) shows enhancement of the t2 hypo - intense areas ( arrow ) .
axial in - phase t1 weighted gradient recalled echo ( gre ) image ( a ) , showing a heterogeneous mass lesion involving the medial portion of the lower pole of the right kidney ( arrow ) , with a posterior isointense area and an anterior area of higher signal intensity , relative to skeletal muscle .
axial fat suppressed t2 ( b ) and coronal ssfse t2 images ( e ) show marked heterogeneity and the 
triple sign ; : areas of low , intermediate and high signal intensity ( arrows ) .
axial post - contrast gre image ( c and d ) shows enhancement of the t2 hypo - intense areas ( arrow ) .
the patient underwent right nephrectomy with a pathological diagnosis of high - grade , poorly differentiated spindle - cell synovial sarcoma .
immunohistochemical staining showed focal positivity for cytokeratin cam 5.2 and negativity for s100 , ck7 , and epithelial membrane antigen ( ema ) .
the most common sarcoma of the kidney is leiomyosarcoma , accounting for 4060% of reported cases .
the first set of 15 cases reported was in 2000 , by argani , with few other cases reported in the english literature .
there have been no reports to date describing the mr imaging findings of primary ss of the kidney .
there is a slight male predominance , with a male - to - female ratio of 1.2 .
furthermore , there seems to be a predilection for the right kidney , with a right - to - left ratio of 2.2 .
the typical presentation of ss of the kidney is non - specific , and resembles that of other primary tumors of the kidney .
patients may complain of localized flank or back pain , hematuria , or a palpable abdominal mass .
the imaging modality of choice is magnetic resonance imaging ( mri ) , given its high sensitivity for soft tissue abnormalities .
although diagnostic for some soft tissue tumors , mr signal intensity characteristics are usually non - specific for ss .
most synovial sarcomas tend to be large masses , averaging 8  cm in size .
the most common mr finding is an oval , well - defined nodular mass . on t1 weighted imaging , small lesions
are typically homogenous , with a signal intensity similar to that of skeletal muscle , while lesions larger than 5  cm often exhibit intermediate intensity signal and are heterogeneous secondary to hemorrhagic and necrotic areas . on t2 weighted imaging , ,
lesions are hyperintense , usually with intratumoral hemorrhage ( 73% ) and cystic components ( 77% ) ; 3557% exhibit the triple sign , showing areas that are hyper- , iso- , and hypo - intense relative to skeletal muscle , representing hemorrhage / necrosis , septa / cellular elements , and calcified / fibrotic areas ; however , this is also seen in other soft tissue tumors , namely malignant fibrous histiocytoma , . mr imaging after intravenous contrast injection shows heterogeneous enhancement .
histologically , ss consists of round spindle cells with minimal cytoplasm and active mitotic figures .
these tumors are further divided into two subtypes , monophasic and biphasic , depending on the absence or presence of a well - develop glandular epithelium .
although , synovial sarcoma in any location is regarded as slow growing , it should be considered a systemic disease .
indeed , 25% have pulmonary metastases at the time of diagnosis . despite wide surgical resection , local recurrence and metastatic disease
however , ss , more than other sarcomas , are more often treated with neoadjuvant chemotherapy followed by surgical treatment .
these tumors demonstrate moderate chemo sensitivity , with 50% response rates to ifosfamide - based or doxorubicin - based regimens .
studies of extremity ss have shown that ifosfamide - based chemotherapy reduces tumor volume by greater than 50% and improves disease - specific survival .
in contrast , renal cell carcinoma is generally considered chemoresistant , although newer drug therapies such as sorafenib and sunitinib have led to some optimism , .
multiple studies of ss of the extremity have shown a strong association between tumor size , volume , and histological grade to disease recurrence and patient mortality .
high grade ss is favored in tumors that exhibit cystic components , hemorrhage , and fluid levels , as well as the triple sign .
 abstractprimary renal synovial sarcoma ( ss ) was first described in 2000 by argani , with only a few subsequent cases being reported in the english literature . 
 herein , we describe a case of a 52-year - old woman who presented with right flank pain . 
 magnetic resonance imaging revealed a 6-cm mass in the lower pole of the right kidney . t1 and t2 weighted imaging revealed a heterogeneous mass with triple sign . 
 there was post - contrast enhancement . 
 imaging , histology and immunostaining together made the diagnosis of ss of the kidney . 
Introduction
Case report
Discussion