Bilateral Tubulocystic Renal Cell Carcinomas in Diabetic End-Stage Renal Disease: First Case Report with Cytogenetic and Ultrastructural Studies
A 62 year-old man with end stage renal disease on hemodialysis due to type II diabetes and hypertension presented with neck and chest pain. A computed tomography (CT) scan to exclude aortic dissection incidentally revealed bilateral complex renal masses less than 3.0 cm in greatest dimension. The patient reported two to three weeks of painless gross hematuria, but denied fever, flank pain, and lower urinary symptoms. Given the patient’s comorbidities and the small size of the lesions, the patient was reluctant to undergo the recommended surgical intervention. Repeat CT scan of the abdomen 5 months later showed relative stability of the lesions with one cyst having grown from 1.1 to 1.3 cm. There was also a small nodular enhancing component considered suggestive of renal cell carcinoma. After an additional 6 months, a complete abdominal CT showed no growth of the cysts but heterogeneous attenuation suggested nodularity or thick septations consistent with malignancy.\nAfter an additional 7 months (18 months after presentation), a repeat CT showed bilateral and multiple enhancing lesions: a 2.6×2.3 cm lesion and a 1.3×1.6 cm lesion in the left mid-kidney, a 1.8×1.7 lesion in the right upper pole, and a 1.5×1.6 cm lesion in the right midkidney (, ). Additional bilateral enhancing lesions did not show interval growth. Cystoscopy and urine cytology at that time were negative for malignancy. A CT urogram showed no excretion of contrast, limiting evaluation of the upper urinary tracts. At that time, with recurrent hematuria, and told of progression of the lesions, the patient elected to undergo bilateral laparoscopic radical nephrectomy.\nThe left kidney and perinephric fat measured 10.5×7.5×4.5 cm and weighed 125.5 grams. The right kidney and perinephric fat measured 11×8×4.5 cm and weighed 190 grams. On cut section, there were multifocal unencapsulated sharply demarcated gray spongy cystic lesions ranging from 0.3 to 2.5 cm in diameter in renal cortex and renal medulla (, ). The cystic lesions contained clear serous fluid. The renal capsules and perinephric fat were grossly uninvolved. Simple cortical cysts were also seen separately. Numerous black multifaceted calculi ranging from 0.1 to 0.2 cm in greatest dimension were present within both renal pelvises (, ). On microscopic examination, the cystic lesions were composed of tightly packed tubules and cysts separated by bland fibrous stroma (). The cysts were lined by a single layer of cuboidal to columnar cells, often with a hobnail appearance. The cells had large round to oval nuclei (Fuhrman grade 2 to 3), prominent nucleoli, and abundant eosinophilic cytoplasm (, ). No desmoplastic reaction or cellular ovarian-type stroma was present. No areas of solid or papillary growth was seen in either kidney. Papillary renal cell carcinoma was not present. Pathologic stage was pT1 for both kidneys.\nImmunostains for vimentin, PAX-2, AE1/AE3, p63, p504S(AMACAR), 34 beta E12, cytokeratin 8/18, EMA, cytokeratin 7, cytokeratin 20, and CD10 were performed using a Dako Autostainer with prior heat induced epitope retrieval in a water bath with buffered Citrate (pH 6.0) and EDTA (pH 8.0) (). The tubulocystic carcinoma cells showed diffuse strong immunoreactivity () for AMACR, AE1/AE3, CK8/18, CD10 and PAX2, and focally strong immunoreactivity for CK7 (), EMA, Vimentin and 34BE12. No immunoreactivity was seen for P63 and CK20. The tubule-containing and cystic areas of the tumor demonstrated equal immunoreactivity for pan-cytokeratin, CK8/18 and AMACR. Immunoreactivity for 34BE12, CK7, CD10 and EMA was greater in the tubule-containing areas, relative to the cystic areas.\nThe uninvolved renal parenchyma bilaterally showed extensive global glomerular sclerosis, interstitial fibrosis, tubular atrophy with thickening of tubular basement membrane, and focal interstitial chronic inflammation. The non-sclerotic glomeruli showed diffuse nodular mesangial expansion, with numerous Kimmelstiel-Wilson lesions highlighted by Periodic Acid Schiff (PAS) stain. Onion-skin thickening of the arterioles was noted. Both kidneys showed multiple simple cysts. Theses changes are consistent with the patient’s clinical history of end-stage renal disease in the setting of hypertension and diabetes.\nFluorescence in situ hybridization (FISH) was performed on a representative section from the left kidney tubulocystic carcinoma using methods described earlier. Briefly, 4.0 micrometer sections from a representative, formalin-fixed, paraffin-embedded block were cut and utilized for FISH studies. To confirm the cytogenetic abnormalities reported previously in a case of TC-RCC, a UroVysion bladder cancer kit containing probes for chromosome 7 (CEP7, spectrum green), and chromosome 17 (CEP17, spectrum aqua) (Abbott Molecular/Vysis Cat. no.36-161070) was used.\nThe FISH data were analyzed using methods described before. The corresponding hematoxylin and eosin slides were reviewed before the FISH study and areas of tumor and normal renal tubules were marked. One hundred nuclei from normal and tumor areas were examined for signals from probes under the fluorescence microscope with 1000 magnification. Normal renal tubules were used as a control. Definitions of chromosomal gain and loss of chromosomes 7, 17 were based on the Gaussian model and related to the non-neoplastic controls. Any tumor with a signal score beyond the cut-off value was considered to have a gain or loss of the specific chromosome. The cut-off values for each probe were set at mean +3 SD of the control values. Gains of chromosomes 7 and 17 were present in 11% and 35% of the tubulocystic RCC cells. Adjacent normal renal tubule cells showed gains of chromosomes 7 and 17 in 1% and 0% of cells, respectively.\nA formalin-fixed sample of the specimen was used for the EM study. The specimen was transferred from neutral buffered formalin to 3% Sorenson’s phosphate buffered glutaraldehyde and washed in 0.1M Sorenson’s phosphate buffer (pH 7.3). The tissue was then post-fixed in 2% osmium tetroxide, dehydrated in a graded series of ethanol. Samples were then transferred to propylene oxide, incubated in mixtures of propylene oxide and eponate 812 (Electron Microscopy Sciences), and embedded in eponate 812 at 60 degrees centigrade. 1.0 micron-thick sections were cut for orientation and 70 nm sections were made for ultrastructural examination. These sections were placed on copper grids and stained with uranyl acetate and lead citrate and examined in a JEM 1010 electron microscope.\nUltrastructural examination revealed the presence of two types of cells. The type I cells () were composed of cuboidal cells bound on their luminal surfaces by tight junctions. The nuclear contour of these cells ranges from irregular () to oval (). Nucleoli were prominent (). There were well-formed brush borders with long microvilli with prominent rootlets (). The cytoplasm of these cells had numerous mitochondria, many of which contained dense plaques (). Lipid material and membrane bound granules were also present. These cells were bound by basement membrane material. Interstitial material consists of fibroblasts, collagen, and blood vessels. These ultrastructural features are characteristic of proximal convoluted tubules. Type I cells were seen in the tubular component of the TCRCC. The type II cells () were present in a single layer, with desmosomal junctions and luminal surfaces bound by tight junctions. The cytoplasm of these cells contained rough endoplasmic reticulum, mitochondria, and lipid droplets. The surfaces of these type II cells were devoid of microvilli (). The base of the glands was bound by basement membrane material. These ultrastructural features are characteristic of distal nephrons. Type II cells were seen in the cystic component of the TC-RCC. No cells had ultrastructural characteristics of both type I and type II cells.\nThe patient died of non-tumor related causes 16 months post-bilateral nephrectomy. No tumor recurrence or metastasis was noted by the time of his death.