metastasis of renal cell carcinoma ( rcc ) to the nasal cavity is an extremely rare occurrence , although rcc is the most common infraclavicular primary tumor that metastasizes to the nasal cavity and paranasal sinuses ( 3 ) . up to the present , 105 cases of maxillary metastases and 21 cases of ethmoid metastases from renal carcinomas have been reported ( 4 ) . we report a case of silent clear cell rcc that presented with epistaxis due to nasal cavity metastasis , followed by a brief review of the relevant literature . a 62-year - old man presented to our ent department with a 3-day history of massive epistaxis of about 300 - 400 ml . he had a past medical history of hypertension and diabetes mellitus , without any abnormal previous nasal or urinary symptoms . the initial laboratory findings showed a low hemoglobin level of 8.0 g / dl ( normal range 13 - 17 g / dl ) but no evidence of thrombocytopenia or coagulopathy , with a platelet count of 330  10/ml ( normal range 130 - 400  10/ml ) , a prothrombin time of 11.7 seconds ( normal range 9 - 13 seconds ) , an international normalized ratio of 1.00 ( normal range 0.7 - 1.20 ) , and activated ptt of 28.4 seconds ( normal range 2 - 37 seconds ) . on nasal endoscopy , a very hyperemic polypoid mass in the right nasal cavity was noted ( figure 1a ) . computed tomography ( ct ) of the paranasal sinuses revealed an approximately 2.2 cm , oval - shaped , soft - tissue - density mass on the pre - contrast images , with avid enhancement in the right ethmoid sinus and nasal cavity ( figure 1b ) . on magnetic resonance imaging ( mri ) , the lesion appeared hyperintense on t2 weighted imaging ( t2wi ) and isointense on t1wi , with strong enhancement ( figure 1c ) . the clinically suspected diagnosis was a hypervascular sinonasal tumor , such as a hemangiopericytoma , hemangioma , or angiofibroma . endoscopic removal of the right sinonasal mass was performed , and the pathology report suggested metastatic clear cell carcinoma of renal origin . workup of the primary tumor was initiated in order to screen the abdomen and the pelvic cavity . on contrast - enhanced 3d ct imaging of the kidneys , a heterogeneously enhancing lobulated mass measuring 9.7  8.5 cm was found in the upper polar region of the left kidney ( figure 1d ) . the low - density central portion of the mass represented necrosis , and prominent collateral vessels were seen around the mass . the anterolaterally displaced left proximal ureter was completely engulfed by tumor , and increased perirenal soft - tissue - density strands suggested perirenal fat invasion . the patient underwent left radical nephrectomy , and the mass was pathologically confirmed as clear cell type rcc . he remained asymptomatic five months after nephrectomy , and is undergoing further follow - up . many ear , nose , and throat ( ent ) problems are observed in general practice , and epistaxis is one of the common chief complaints of visiting patients . when an underlying hypervascular mass is detected in the nasal cavity or paranasal sinuses , a primary sinonasal tumor is first suspected , such as angiofibroma , hemangiopericytoma , hemangioma , or sinonasal glomus tumors ( 5 ) . however , a small minority of patients who present with epistaxis show a metastatic secondary sinonasal mass . therefore , vascular malignant lesions , such as adenocarcinomas , melanomas , and other metastatic tumors from primary sites arising below the level of the clavicle should be considered . lung , breast , and renal cell carcinomas are common neoplasms that metastasize to the head and neck region ; most of these metastases occur in the thyroid gland . however , rcc is the most frequent infraclavicular tumor to metastasize to the nasal cavity and paranasal sinuses ( 6 ) . therefore , high suspicion and detection of a secondary nasal mass as the cause of epistaxis , and identification of the primary site of origin , are important in cases of unusual or uncontrolled epistaxis , and rcc metastasis should be included in the differential diagnosis of nasal bleeding lesions . the most common histologic subtype is clear cell rcc ( 85% ) ( 7 ) . clear cell rcc is known to be associated with loss of function of the von hippel - lindau gene , which upregulates hypoxia - induced factor ( hif ) , finally increasing the function of vascular endothelial growth factor ( vegf ) . this sequence of events eventually increases the angiogenesis and vascularity of clear cell rccs and related metastases . it has been accepted that rcc tumor cells spread to the sinonasal region via two potential hematogenous routes : one bypassing pulmonary capillary filtration and the other leading directly to the head and neck region via extensive anastomosis between the avalvular vertebral venous plexus and the intracranial venous plexus ( 8) . the tumor cells spread on the first route via the classical pathway through the inferior vena cava , lungs , heart , and maxillary artery ; in these cases , concurrent lung or brain metastases may be present . the second route is via the vertebral plexus , in which tumor cells do not enter the inferior vena cava but travel through the vertebral venous plexus , the intracranial venous plexus , and the cavernous venous plexus via venous anastomoses , to reach the nasal and paranasal sinuses . in these cases , many rccs grow slowly , and only manifest after a considerable tumor size is reached , usually with the classical presentation of flank pain , palpable flank mass , or gross hematuria . since symptoms of metastatic tumors often precede those of the primary tumor in renal cancer , when a patient presents with a mass in the sinonasal region , the possibility of a metastatic secondary mass , especially of renal origin , should be considered even in the absence of a past history of renal cancer . the prognosis of patients with metastatic rcc is poor , with a median survival of 7 - 11 months . in addition , metastatic rcc is resistant to chemotherapy and radiotherapy , although a variable response has been reported ( 9 ) . many metastatic tumors of renal origin develop in multiples , such as in the lung or liver , but most metastatic tumors in the sinonasal region are single . therefore , a patient with a single , resectable , metastatic rcc in the sinonasal cavity may benefit from surgical intervention , and should be treated aggressively with metastasectomy and primary tumor resection . the case described here is unusual because the presence of a primary tumor was unclear , and because of the unusual metastatic site . early diagnosis and surgical removal of both primary and metastatic tumors is important in order to prolong the patient s life . when a patient presents with a mass in the nasal or paranasal sinus region , the possibility of metastatic renal cell carcinoma should be considered .
the paranasal sinuses are known to be a rare location for metastasis . 
 renal cell carcinoma ( rcc ) is the most frequent primary tumor to metastasize to the sinonasal region , followed by lung and breast cancer . in particular , 
 clear cell type rcc , which represents approximately 85% of rccs , is characterized by early metastasis , and it sometimes spreads to unusual sites ( 1 , 2 ) . metastatic tumors in the paranasal sinuses are distributed in the maxillary , sphenoid , ethmoid , and frontal sinuses , in order of decreasing frequency . 
 symptoms are usually nonspecific , but epistaxis is the most common sign , due to the hypervascularity of the primary tumor . the prognosis is uncertain , but the 5-year survival rate fluctuates between 15% and 30% . 
 the purpose of this case report is to document a rare case of silent rcc that first presented as epistaxis due to nasal cavity and ethmoid sinus metastasis .