patients are often asymptomatic and the anomaly is discovered during imaging studies carried out for other reasons . however ,
when symptoms are present , they are related to hydro - nephrosis , infection , or calculus formation .
the incidence of renal tumor in a horseshoe kidney is higher than in normal population . we present a case of renal cell carcinoma ( rcc ) in a horseshoe kidney .
presence of the kidney malformation can change the surgery plan for preserving the organ without removing any functional tissue .
a 62-year - old male patient presented to our institute , as a referral case from another hospital , with an abdominal mass .
computed tomography ( ct ) scan of abdomen and pelvis was performed utilizing routine ct renal mass protocol .
the scan revealed presence of a horseshoe kidney anomaly with a well - enhanced isthmus [ figure 1a ] . by using a power injector
, we administered 150 ml of intravenous contrast material at a minimum rate of 3 ml / s . using , a multi - detector row ct scanner , contrast material - enhanced imaging was performed during the corticomedullary and nephrographic phases of enhancement using scanning delays of 40 s and 100 s , respectively .
large lobulated mass was identified in the left side of the horseshoe kidney associated with an area of central cystic necrosis .
the mass measured about 12 cm  13 cm  15 cm in anterior - posterior , width , and crainio - caudal maximum dimensions , respectively [ figure 1b and c ] .
the renal vein and intravenous vena cava were patent and there was no evidence of significant enlarged intra - abdominal lymph nodes .
the diagnosis made was rcc with a horseshoe kidney and patient was sent for urology consultation and surgical resection .
( a - c ) ct scan images of the abdomen obtained at the level of inferior mesenteric artery .
( a ) before administration of the contrast material shows a horseshoe kidney anomaly ( arrow ) .
post - contrast images in b ) axial and c ) coronal planes show a large mass arising from the left part of the horseshoe kidney ( arrow ) .
the mass is multi - lobulated and heterogeneous in attenuation with a central area of cystic necrosis hemi - nephrectomy was performed at our institute .
follow - up ct scan of the abdomen and pelvis obtained in the post - operative period revealed resection of the previously described large mass within the left part of the horseshoe kidney .
single selected axial computed tomography scan image of the abdomen performed in the post - operative period shows resection of the large mass in the left part of the horseshoe kidney with organ preserving surgery .
the surgically removed gross specimen was a large mass , which had replaced more than 2/3 of the left side of the horseshoe kidney .
the mass was lobulated and variegated , ranging from tan and yellow to dark brown .
pathology specimen shows a large multi - lobulated mass associated with an area of hemorrhage and cystic necrosis .
hematoxylin - eosin ( h and e ) stained histology slides of the above described mass revealed clear cell rcc with prominent borders and profuse network of small , thin - walled sinusoid - like blood vessels [ figure 4a and b ] .
hematoxylin and eosin stained slides of the clear cell renal cell carcinoma ( rcc ) mass in a horseshoe kidney .
( a ) at 6 magnification shows the tumor margin ( arrow ) in relation to the reminder of the kidney , ( b ) at 300 shows clear cells with prominent cell borders ( black arrow ) and vascularity ( yellow arrow )
no genetic determinant is known , although , it has been reported in identical twins and in siblings within the same family .
horseshoe kidney consists of two distinct functioning kidneys on each side of the mid - line , connected at the lower poles by an isthmus of functioning renal parenchyma or fibrous tissue that crosses the mid - line of the body .
nearly , one - third of all patients with a horseshoe kidney remain asymptomatic and the pathology is discovered incidentally during physical examination or ct and ultrasound scans .
when symptoms are present , they are related to hydro - nephrosis , infection , or calculus formation .
the incidence of renal tumor in a horseshoe kidney is approximately 3 to 4 times greater than in normal population , and is possibly the result of chronic obstruction , lithiasis , and infection .
the tumor can localized at any part of the kidney but it mostly found within the isthmus .
ct utilizing routine renal mass protocol is the primary imaging modality of choice for localization and staging of any renal tumor .
however , in case of rcc and horseshoe kidney , ct angiography is highly recommended to check the renal vascularity , which generally varies and is essential for pre - operative planning .
if ct scanning is performed specifically to evaluate a known renal mass , the study must include an unenhanced examination prior to the administration of intravenous contrast material .
after administration of contrast , scans are taken at intervals of 40 s and 100 s during the enhancement phase .
the dataset can be manipulated by using a 3d workstation to produce volume - rendered and 3d images when necessary .
it is becoming increasingly important for radiologists to produce 3d reconstructed images as more laparoscopic surgery is being performed for the treatment of renal cancer , and these images are helpful in such procedures .
thus , pre - operative surveillance is highly recommended for early identification of metastatic activity and positive surgical margin .
surgical approach is through the mid - line in order to have better exposure of the isthmus for isthmectomy .
clear cell rcc , the pathology subtype , as found in our case , is typically a solitary tumor and the tumor commonly presents as bosselated , well - circumscribed mass with fibrosis and with a capsule or pseudo - capsule .
lipid - rich cells in clear rcc impart the classical golden yellow color seen on gross pathology analysis .
clear cell rcc may exhibit a variety of histo - architectural patterns including , solid , alveolar , and acinar forms .
horseshoe kidney is the most common renal fusion anomaly and is more predominate in males and it is detected mostly as incidental finding on ct or us examination .
rcc is one of the malignancies associated with this malformation , as was seen in our case .
 renal cell carcinoma ( rcc ) is encountered in about 3% of all adult neoplasms . 
 presence of any kidney malformation can change the plan for surgical treatment of rcc with organ preserving surgery . 
 we report a case of clear cell rcc in a horseshoe kidney . 
 computed tomography scan revealed a horseshoe kidney anomaly with a large mass in the left side . 
 the diagnosis of rcc was confirmed by pathology and histology findings . 
INTRODUCTION
RADIOLOGICAL FEATURES
PATHOLOGICAL FEATURES
DISCUSSION
CONCLUSION