hepatocellular carcinoma ( hcc ) is one of the most common malignancies globally and accounts for nearly 1 million new cases per year . the most frequent metastatic sites for hcc include the lung , lymph nodes , bones , and adrenal glands . primary tumors that commonly metastasize to the kidney are lung ( 19.8% ) , breast ( 12.3% ) , stomach ( 11.1% ) , and contralateral kidney ( 8.6% ) tumors . the incidence of de novo hcc after an orthotopic liver transplant ( olt ) is extremely rare , with an estimated incidence of 25 per 100,000 person - years . thus , two rare events occurred in the same patient in the present case report , with a further anomaly being the lack of an obvious primary liver hcc at the time of the radical nephrectomy . here we report this case of renal metastasis of hcc arising in the recipient 's transplanted liver 10 years after transplantation for cryptogenic cirrhosis . a 70-year - old man presented with an incidental right renal mass after magnetic resonance cholangiopancreatography ( mrcp ) for investigation of abnormal results of liver function tests ( lfts ) , which suggested an obstructed biliary tree . the patient had undergone olt in 2000 after extensive preoperative investigations for cryptogenic liver cirrhosis including serology and radiology . post - olt histopathology showed that the native liver had nodules of varying sizes consistent with cirrhosis with no evidence of carcinoma . the patient was started on immunosuppressive therapy with tacrolimus , which was subsequently changed to sirolimus in 2005 , and he was followed up quarterly by the liver transplant service at our center . on routine follow - up , the patient was found to have obstructive ( cholestatic ) lft results in late 2009 . an mrcp was performed and a diagnosis of choledocholithiasis was made , but incidentally a right renal mass was also found . a triple - phase computed tomographic ( ct ) scan of his abdomen and pelvis further confirmed the presence of a lobulated enhancing mass ( 55 mm45 mm in diameter ) in the right upper pole extending into the perinephric fat and abutting the right hemidiaphragm ( fig . 1a , b ) but with a clear plane between the liver and the mass . his case was reviewed at a multidisciplinary meeting where consensus dictated that the mass was likely to represent a primary renal tumor that should be resected . the patient underwent a right open radical nephrectomy via a flank approach and resection of part of the hemidiaphragm requiring repair with a synthetic mesh ( gore - tex patch ) . 2 ) invading the upper pole of the kidney , perinephric fat , and diaphragm . immunohistochemical staining ( positive for heppar 1 and polyclonal carcinoembryonic antigen ) was also suggestive of hcc . the patient was discharged but 5 months later it was noted that his serum alpha - fetoprotein levels were significantly elevated and abnormal serum baseline liver function was declining . a ct scan further confirmed the liver lesions , which continued to enlarge ( fig . after a multidisciplinary meeting , the patient was commenced on the tyrosine kinase inhibitor sorafenib in a bid to control his overt metastatic disease , which at 3 months has stabilized . . primary tumors of the lung , breast , and gastrointestinal tract are the most common sources of renal metastases . other sources include the cervix , prostate , gall bladder , thyroid , ovary , testis , urinary bladder , contralateral kidney , and bone . renal metastasis , however , is an uncommon site for hcc . in a search of the literature using medline , embase , and google scholar with cascading from returned manuscripts , we found fewer than 15 reported cases of hcc with renal metastasis in a living patient . increased risk of de novo malignancies is a serious long - term complication following liver transplantation . nonmelanoma skin malignancies are the most frequent types of cancer occurring in the post - olt setting , with age , cumulative years after olt , and use of immunosuppression as independent risk factors . what was interesting about our case was that our patient underwent liver transplant for cryptogenic cirrhosis after an extensive preoperative workup to exclude hcc . histological examination of the native liver was also confirmed to show only cirrhosis without any evidence of carcinoma . the patient was also on tacrolimus after olt for 5 years and then switched to sirolimus . although the role of systemic immunosuppression in promoting posttransplant tumors is not clearly defined , clinical evidence supports the effect of cyclosporine and tacrolimus in impairing cellular immunity and tumor cell surveillance at the time of liver transplantation . an elevation in tumor incidence was also observed in liver transplant patients on either tacrolimus- or cyclosporine - based regimens . needle biopsies performed under ct guidance appear to be safe ( with a minimal risk of bleeding or of seeding of the needle tract with malignant cells ) , and they have a sensitivity for the detection of cancer of 80% to 92% and a specificity of 83% to 100% . we do not routinely biopsy lesions that will definitely undergo surgery as in this case , and although it may have been useful to know , his staging and in particular liver imaging was negative and he had no prior history of malignancy . thus , we do not believe biopsy would have changed his management . flemming et al .   reported a case of hcc originating from the donor liver that was identified by an allelic pattern of the donor and the recipient . saxena et al .   also confirmed the de novo origin of hcc by the difference in the donor 's sex chromosome from that of the recipient . although we did not perform such genetic analysis , the clinical course of the patient is highly suggestive of hcc that arose in the donor allograft . in conclusion , a differential diagnosis of metastatic hcc should be kept in mind in a patient presenting with a renal mass with history of liver transplantation and immunosuppression . however , in reality , this is rare and perhaps if any lesions in the liver are present , including small ones , a biopsy should be considered . if nephrectomy is considered , the surgery may be more extensive in the case of metastatic disease but is certainly possible with the involvement of hepatobiliary surgeons , particularly where liver involvement is suspected .
urological involvement of hepatocellular carcinoma ( hcc ) is rare ; hcc arising in an orthotopic liver transplant ( olt ) is exceptionally rare . 
 here we report the case of a 70-year - old man who was incidentally found to have metastatic hcc in the right kidney arising from his olt undertaken for cryptogenic cirrhosis 10 years previously . 
 adding to the complexity of this case was the lack of an obvious liver primary hcc at the time of the radical nephrectomy , thus making the final diagnosis all but impossible . 
 we believe this report represents the first report of hcc metastasizing to the kidney after olt and adds to the few reports in the literature of hcc arising in transplanted livers .