High-resolution analysis of DNA copy number alterations and gene expression in renal clear cell carcinoma

We analysed chromosomal copy number aberrations (CNAs) in renal cell carcinomas by array-based comparative genomic hybridization, using a genome-wide scanning array with 2304 BAC and PAC clones covering the whole human genome at a resolution of roughly 1.3 Mb. A total of 30 samples of renal cell carcinoma were analysed, including 26 cases of clear cell carcinoma (CCC) and four cases of chromophobe renal cell carcinoma (ChCC). In CCCs, gains of chromosomes 5q33.1-qter (58%), 7q11.22-q35 (35%) and 16p12.3-p13.12 (19%), and losses of chromosomes 3p25.1-p25.3 (77%), 3p21.31-p22.3 (81%), 3p14.1-p14.2 (77%), 8p23.3 (31%), 9q21.13-qter (19%) and 14q32.32-qter (38%) were detected. On the other hand, the patterns of CNAs differed markedly between CCCs and ChCCs. Next, we examined the correlation of CNAs with expression profiles in the same tumour samples in 22/26 cases of CCC, using oligonucleotide microarray. We extracted genes that were differentially expressed between cases with and without CNAs, and found that significantly more up-regulated genes were localized on chromosomes 5 and 7, where recurrent genomic gains have been detected. Conversely, significantly more down-regulated genes were localized on chromosomes 14 and 3, where recurrent genomic losses have been detected. These results revealed that CNAs were correlated with deregulation of gene expression in CCCs. Furthermore, we compared the patterns of genomic imbalance with histopathological features, and found that loss of 14q appeared to be a specific and additional genetic abnormality in high-grade CCC. When we compared the expression profiles of low-grade CCCs with those of high-grade CCCs, differentially down-regulated genes tended to be localized on chromosomes 14 and 9. Thus, it is suggested that copy number loss at 14q in high-grade CCC may be involved in the down-regulation of genes located in this region.     

转移性透明细胞性肾细胞癌42例临床病理分析

目的探讨转移性透明细胞性肾细胞癌(clear cell renal cell carcinoma,CCRCC)的临床病理学特征、诊断及鉴别诊断。方法回顾性分析42例转移性CCRCC的临床病理资料,并复习相关文献。结果 42例转移性CCRCC中,男性35例,女性7例;转移部位依次为肺19例,骨8例,淋巴结及软组织各3例,肾上腺、皮肤及脑各2例,肝、小肠及鼻腔各1例。42例转移性CCRCC中,31例于肾原发灶手术切除后3周~11年出现转移,4例原发灶与转移灶同时发现;28例转移灶为单发,14例为多发性。34例转移性CCRCC仍具有原发性CCRCC的组织学形态,4例出现多灶状坏死,6例呈肉瘤样分化。Fuhrman细胞核分级:Ⅰ级4例、Ⅱ级13例、Ⅲ级18例、Ⅳ级7例。17例间质小血管呈簇状增生。免疫组化标记42例转移性CCRCC中CD10、vimentin、CAⅨ、PAX8、RCC和EMA阳性例数分别为39例(92.9%)、40例(95.2%)、38例(90.5%)、38例(90.5%)、31例(73.8%)和38例(90.5%)。结论转移性CCRCC具有独特的临床病理学特征,结合临床病史及肿瘤组织形态学特点,联合免疫组化标记vimentin、EMA、CD10、CAⅨ、PAX8等有助于诊断及鉴别诊断。     

FHIT expression in clear cell renal carcinomas: versatility of protein levels and correlation with survival

Clear cell renal cell carcinomas (RCCs) are characterized by a deletion of chromosome 3p, which might result in the inactivation of the FHIT (fragile histidine triad) gene, a putative tumour suppressor gene. To explore the relevance of FHIT aberrations for tumour progression and prognosis in clear cell RCCs, FHIT protein expression was analysed in formalin-fixed tissue from 149 clear cell RCCs by immunohistochemistry. FHIT protein expression was found to be markedly reduced in all RCCs, when compared with adjacent non-neoplastic tubule epithelia. Although remaining below the FHIT levels of normal tubule epithelia, a significant increase of FHIT expression became evident from well (G1) to poorly (G3) differentiated clear cell RCCs (p=0.0001) and from low (pT1) to advanced (pT3) tumour stages (p=0.001). The log-rank test demonstrated a significant inverse correlation (p=0.0074) between FHIT expression and tumour aggressiveness as indicated by patient survival. Cox regression analysis revealed that FHIT expression is an independent prognostic parameter (p=0.0139) in clear cell RCCs. In conclusion, clear cell RCCs show a marked reduction of FHIT protein expression when compared with their putative cells of origin. In contrast to other tumour types, however, loss of FHIT protein expression is significantly less pronounced in poorly differentiated RCCs or advanced tumour stages. This versatility of FHIT expression during tumour progression suggests a role for reversible mechanisms of FHIT inactivation during the initiation and progression of clear cell RCCs.     

肾透明细胞癌伴同侧肾上腺皮质腺瘤内转移1例及文献复习

目的：探讨1例肾透明细胞癌(clear-cell renal cell carcinoma,clear-cell RCC)伴同侧肾上腺皮质腺瘤内转移的临床病理特征及转移机制。方法：观察1例肾透明细胞癌转移至同侧肾上腺皮质腺瘤的临床表现、组织学特征、免疫组织化学特点,并复习相关文献。结果：患者,男性,63岁,右季肋部不适半月余入院。术后结果显示右肾透明细胞癌。单纯性孤立性肾囊肿。右肾上腺皮质腺瘤,瘤内见转移的肾透明细胞癌、直径约3 mm。结论：肾透明细胞癌转移至同侧肾上腺皮质腺瘤是非常罕见的现象。     

Cutaneous metastasis of renal cell carcinoma: a report of two cases

Cutaneous metastasis of renal cell carcinoma (RCC) is very rare. The author herein report two cases of RCC with cutaneous metastasis. Case 1: is a 75-year-old man with right lumbago. Imaging modalities including CT and MRI revealed a right renal tumor. Nephrectomy was performed. Pathological diagnosis of the renal tumor was RCC of clear cell type (Fuhrman's grade II). He denied follow-up. Nine years later, he (at the age of 84 years), a neck skin tumor emerged. Clinical diagnosis was hemangioma. Imaging modalities including CT and MRI showed several tumors in both lungs. The resection of the neck tumor was performed. The tumor was composed of clear cell type arranged in a trabecular pattern. Immunohistochemically, the tumor cells were positive for pancytokeratins, cytokeratin 18, CD10, Ki-67 (labeling=13%), but negative for CD34, factor-VIII-related antigen, CEA, EMA, melanosome (HMB45), S100 protein, p53, and HepPar-1. Metastatic RCC was diagnosed. Despite interferon therapy, he died of 6 months after the second admission. Case 2 is a 66-year-old man with gross hematuria. Imaging modalities revealed left renal tumor. A nephrectomy was performed. The pathological diagnosis was RCC of clear cell type (grade II). The tumor was invasive into the renal pelvis. He was treated by chemoradiation, but metastases of lungs, skin (thigh), and lib emerged, and died of cachexia 9 months after the admission. Necropsy of the skin tumor was performed. The skin tumor was composed of clear cells arranged in a trabecular pattern. Immunohistochemically, the tumor cells were positive for pancytokeratins (AE1/3, CAM5.2), CD10, p53, and Ki-67 (labeling=20%), but negative for CD34, factor-VIII-related antigen, CEA, melanosome (HMB45), S100 protein, and HepPar-1. A diagnosis of RCC (grade II) was diagnosed.     

Large-scale molecular and tissue microarray analysis of mesothelin expression in common human carcinomas

The 40-kilodalton processed glycoprotein, mesothelin, is highly expressed in epithelial mesotheliomas and adenocarcinomas of the ovary (serous papillary) and pancreas, but its expression in a large series of other common carcinomas has not been completely explored. In the present study, we used oligonucleotide and tissue microarrays to profile the expression of the mesothelin gene (MSLN) and encoded protein, respectively. Among 150 carcinomas of multiple anatomic sites, we found the highest average expression of MSLN in serous carcinomas of the ovary and adenocarcinomas of the pancreas, consistent with previous reports, as well as measurable but less-striking expression in pulmonary, gastric/esophageal, and colorectal adenocarcinomas. On tissue microarrays containing 621 carcinomas derived from the same and additional sites as those profiled by gene expression, mesothelin immunoreactivity was highest in cancers of the ovary (serous papillary, endometrioid, and undifferentiated) and pancreas, with less frequent staining seen in adenocarcinomas of the endometrium, lung, and stomach/esophagus. Some immunopositivity was observed in 42% of pulmonary adenocarcinomas, including 18% that had >50% of tumor cells that were immunoreactive. Some 14% of breast and 30% of colorectal adenocarcinomas showed immunopositivity, but no case contained >50% tumor cells that were immunoreactive. Mesothelin was either entirely absent or present in <5% of carcinomas of the prostate, bladder/ureter, liver, kidney, and thyroid. Overall, we observed good concordance between the results obtained by oligonucleotide and tissue microarrays. This large study of the MSLN gene and protein expression in common carcinomas provides data for future investigations that evaluate the utility of mesothelin/megakaryocyte potentiating factor as a potential serum tumor marker or target of immunotoxin-based therapy in human cancers.     

Circulating tumour tissue fragments in patients with pulmonary metastasis of clear cell renal cell carcinoma

Tumour metastasis is the result of a complex sequence of events, including migration of tumour cells through stroma, proteolytic degradation of stromal and vessel wall elements, intravasation, transport through the circulation, extravasation and outgrowth at compatible sites in the body (the ‘seed and soil’ hypothesis). However, the high incidence of metastasis from various tumour types in liver and lung may be explained by a stochastic process as well, based on the anatomical relationship of the primary tumour with the circulation and mechanical entrapment of metastatic tumour cells in capillary beds. We previously reported that constitutive VEGF‐A expression in tumour xenografts facilitates this type of metastatic seeding by promoting shedding of multicellular tumour tissue fragments, surrounded by vessel wall elements, into the circulation. After transport through the vena cava, such fragments may be trapped in pulmonary arteries, allowing them to expand to symptomatic lesions. Here we tested whether this process has clinical relevance for clear cell renal cell carcinoma (ccRCC), a prototype tumour in the sense of high constitutive VEGF‐A expression. To this end we collected and analysed outflow samples from the renal vein, directly after tumour nephrectomy, in 42 patients diagnosed with ccRCC. Tumour fragments in venous outflow were observed in 33% of ccRCC patients and correlated with the synchronous presence or metachronous development of pulmonary metastases (p < 0.001, Fisher's exact test). In patients with tumours that, in retrospect, were not of the VEGF‐A‐expressing clear cell type, tumour fragments were never observed in the renal outflow. These data suggest that, in ccRCC, a VEGF‐A‐induced phenotype promotes a release of tumour cell clusters into the circulation that may contribute to pulmonary metastasis. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Thyroid metastasis of clear cell renal carcinoma: Report of a case

Renal cell carcinoma can recur many years after diagnosis and nephrectomy metastasizing even in uncommon sites, including thyroid gland. Thyroid metastases are extremely rare, the most frequent site of origin are renal tumors. Metastases in thyroid gland appear as painless nodules or masses, “cold” at scintiscan. We report the case of a 67‐year‐old male patient affected by clear cell renal carcinoma, diagnosed by fine‐needle aspiration cytology procedures, and treated with anticancer medical therapy, who noticed after some months a mass in the neck‐thyroid region requiring deeper medical investigations. By this way, thyroid fine‐needle aspiration cytology reported a lesion made of malignant epithelial cells compatible with metastases of renal carcinoma (clear cell). Clinical and pathological data, together with immunostaining, supported the diagnosis of metastatic clear cell renal carcinoma. The diagnosis of metastatic disease, although difficult clinically and pathologically, should be suspected in patients with a clinical history of cancer, particularly in case of renal cell carcinoma, but fine‐needle aspiration cytology can provide the clue for diagnosis. Diagn. Cytopathol. 2009. © 2009 Wiley‐Liss, Inc.     

Expression of secretagogin in clear-cell renal cell carcinomas is associated with a high metastasis rate

Renal cell carcinomas are divided into several subgroups according to their histopathologic characteristics. The outcome, therapy responses, and the applicability of molecular-targeted therapies depend on the tumor classification and on the tumor stage. Recent advances within the biomarker research facilitated the exact classification of the molecular character of the renal tumor. For example, the calcium-binding proteins parvalbumin and S-100A1 are characteristically expressed in renal cell carcinoma subgroups. This led us to investigate the expression of the novel calcium-binding protein secretagogin in renal cell carcinomas. Tissue microarray cylinders including 94 clear-cell renal cell carcinomas, 61 non-clear-cell renal cell carcinomas (37 papillary renal cell and 24 chromophobe carcinomas), and 30 oncocytomas were analyzed by immunohistochemistry. This showed remarkable secretagogin expression in 37% of the clear-cell renal cell carcinomas. Non-clear-cell renal cell carcinomas and oncocytomas were completely negative. Consequently performed immunoblotting analyses confirmed this expression profile. Because publicly available data direct toward a formation of a hierarchical cluster of secretagogin overexpressing clear-cell renal cell carcinomas, we conducted a clinical follow-up of the patients with clear-cell renal cell carcinoma. This revealed significantly more metastasis within the secretagogin-positive clear-cell renal cell carcinoma subgroup (49% versus 28%; P < .05). In conclusion, we report on detection of the novel calcium-binding protein secretagogin within a subgroup of clear-cell renal cell carcinomas. The increased metastasis rates within the secretagogin-positive subgroup of clear-cell renal cell carcinomas direct toward a clinical impact of our findings.     

Increased RANKL expression is related to tumour migration and metastasis of renal cell carcinomas

Receptor activator of NF‐κB ligand (RANKL) and its receptor, receptor activator of NF‐κB (RANK), play a key role in osteoclastogenesis, and osteoprotegerin (OPG) acts as a decoy receptor for RANKL. We investigated the role of the RANKL–RANK–OPG system in renal cell carcinomas (RCCs), which frequently metastasize to bones. Real‐time quantitative PCR revealed that RANKL mRNA expression was higher in clear cell RCCs than in papillary and chromophobe RCCs. Similarly, RANKL protein expression level in clear cell RCCs was higher than that in papillary and chromophobe RCCs, showing positive correlations with the primary tumour stage and distant metastasis. There was no significant association between the expression level of RANK, OPG and histological subtypes of RCC. RANKL and RANK expression was observed in metastatic RCCs in the bone and other organs, suggesting that they play a role in metastasis to the bone and other organs. Recombinant RANKL protein stimulated migration of a clear cell RCC cell line, Caki‐1, in vitro, and this enhanced migration was inhibited by the administration of recombinant OPG protein. Furthermore, multivariate Cox analysis revealed that elevated RANKL and RANK expression with low‐OPG expression was a significant and independent predictor of recurrence, bone metastasis and a poor prognosis. These data suggest that the RANKL–RANK–OPG system is involved not only in the bone metastasis of RCCs but also in metastasis to other organs through the stimulation of cancer cell migration. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Lack of KISS1R expression is associated with rapid progression of conventional renal cell carcinomas

The mortality of patients with conventional renal cell carcinomas (RCC) correlates directly with the development of metastasis, which cannot be reliably predicted simply by TNM classification. The aim of this study was to identify genes associated with the tumour progression. We have analysed the global gene expression in conventional RCCs, including those with and without progression by Affymetrix GeneChip and selected the genes by gene set enrichment analysis. The expression and function of KISS1R was validated by RT-PCR, western blotting and immunohistochemistry and by in vitro experiments. An immunohistochemical and clinical follow-up study showed that lack of KISS1R expression is associated with rapid progression of tumours. In vitro studies showed that activation of KISS1/KISS1R signalling by kisspeptin treatment decreases the motility and invasive capacity of tumour cells. The kisspeptin treatment also induces the expression of KISS1R in tumour cells in vitro and activates signalling in cases without constitutional expression of the receptor. Expression of the KISS1R protein can be used for estimating the prognosis of conventional RCCs. Confirming the activation of KISS1R signalling in vivo may open a way for kisspeptin treatment of patients with conventional RCCs.     

Clear-cell papillary renal cell carcinoma: 24 cases of a distinct low-grade renal tumour and a comparative genomic hybridization array study of seven cases

Adam J, Couturier J, Molinié V, Vieillefond A & Sibony M
(2011) Histopathology 58, 1064–1071
Clear‐cell papillary renal cell carcinoma: 24 cases of a distinct low‐grade renal tumour and a comparative genomic hybridization array study of seven cases Aims: To report clinicopathological and genomic characteristics of (ccpRCC), a rare, recently characterized renal tumour entity. Methods and results: Twenty‐four renal tumours identified as ccpRCC were collected. Data from comparative genomic hybridization on microarrays (array‐CGH) were obtained for seven of these. Most tumours (58%) occurred in the absence of renal disease. Mean patient age was 58.1 years. Tumours were small (mean size: 2.4 cm) and classified as pT1. Histological characteristics consisted of tubules and papillae lined by a single layer of small clear cells harbouring low‐grade nuclei (Fuhrman grades 1 or 2). Architectural variations, with compact areas (41% of cases) and a micro‐ or macrocystic pattern (67% of cases) were observed frequently. Immunostaining demonstrated diffuse, strong expression of cytokeratin 7 and vimentin, whereas CD10, racemase, RCC antigen, translocation factor E3, TFE3 and translocation factor EB were consistently negative. In seven tumours, array‐CGH detected no chromosomal imbalances. Conclusions: Clear‐cell papillary renal cell carcinoma (ccpRCC) were differentiated from other renal neoplasms by a specific constellation of histopathological and immunohistochemical features, without characteristic genomic imbalances. Clinical, histopathological and genomic data suggested that these tumours have a low potential for malignancy.     

Correlation of very late activation integrin and CD44 expression with extrarenal invasion and metastasis of renal cell carcinomas

Cell adhesion molecules mediate cell-cell and cell-matrix interactions, and they are thought to play an important role in tumor invasion and metastasis. Altered expression of integrins and CD44 in renal cell carcinoma has been recently demonstrated, but an association with invasive or metastatic behavior has not been reported. We examined very late activation (VLA) integrin and CD44 expression in 37 renal cell carcinomas and correlated adhesion molecule expression with multiple histological and clinical parameters. Most tumors exhibited positive staining for VLA3 (81%). Approximately one third of the tumors stained positively for VLA6 and CD44, and fewer (27%) were positive for VLA2. Only a few tumors were positive for VLA4 (8%) and VLA5 (14%). Most of the tumors exhibiting positive staining showed a combination of membranous and cytoplasmic staining patterns. Low-grade tumors positive for VLA6 showed a tendency for basilar staining of the tumor cells, whereas high-grade tumors exhibited diffuse cytoplasmic staining. All tumors exhibiting weak or strong positive staining for VLA4 or VLA5 showed extrarenal invasion or were known to have developed metastases at the time of nephrectomy. All tumors strongly positive for VLA2 or CD44 showed invasion beyond the renal capsule or metastases. In contrast to a previous study, no association was observed between positive staining and tumor grade. Nor were tumor size, architectural pattern, cell type, or DNA ploidy found to be associated with particular staining patterns. Although many of the invasive tumors showed no difference in VLA integrin or CD44 expression compared with tumors confined to the kidney, increased expression in some of them suggests that these cell adhesion molecules may contribute to the invasive or metastatic phenotype.     

Simultaneous double primary clear cell carcinomas of liver and kidney: a case report and review of literature

Reported herein are simultaneous double primary clear cell carcinomas arising from liver and kidney. A 63-year-old man underwent a partial wedge nephrectomy of the right kidney in a surgical resection for hepatocellular carcinoma. Coincidently, on histology the tumors in liver and kidney were consisted of clear cancer cells, which arranged in haphazardly intermixed pattern without capsules. Immunohistochemically, the clear neoplastic cells in the liver were positive for HepPar-1, GPC3, and negative for nephrogenic markers; however, renal clear neoplastic cells were positive for CD10, RCC and Pax-8, but negative to liver-derived markers. These findings led to the diagnosis of simultaneous double primary clear cell carcinomas of kidney and liver. Multiple primary carcinomas of kidney and liver, especially both are primary clear cell carcinomas, are extremely rare neoplasms, only 1 case has been reported previously until now. To our knowledge, this is a report of multiple primary carcinomas arising from the liver and kidney and reminders us of differentiation diagnosis with carcinoma metastasis.     

Clear cell type of renal cell carcinoma with numerous hyaline globules: a diagnostic pitfall

A unique and never-before-published example of clear cell renal cell carcinoma (CRCC) found among 9000 primary renal cell tumors is presented. The tumor contained such a dense concentration of glassy hyaline globules (GHG) in the cytoplasm of the neoplastic cells that it overshadowed the morphology of the neoplasm. The resulting appearance of the tumor was quite misleading and different from the conventional CRCC. The GHG were 7-30 microm in diameter. They were glassy and pale to slightly eosinophilic in color in hematoxylin-eosin. The GHG stained positively with periodic acid-Schiff and negatively with silver and Hale's colloidal iron. Immunohistochemically, they were also negative for anti Mycobacterium bovis antigen. At the ultrastructural level, the GHG were formed by an amorphous mass of stellate shape. The GHG were localized within rough endoplasmic reticulum. Molecular genetically, mutation of the distal part of exon 3 of the VHL gene causing elongation of the VHL protein was found in the tumor, thus confirming the diagnosis of CRCC.     

Tumour-to-tumour metastasis: a rare cause of apparent intratumoural heterogeneity in conventional clear cell renal cell carcinoma

Tumour-to-tumour metastasis is a rare phenomenon and few case reports exist that describe tumor-to-tumor metastases to and from clear cell renal cell carcinoma.¹ In order for metastases to become established, tumour cells must be shed, survive in circulation, and implant, grow, and establish vascularity in a distant site - which in our case was within another primary tumour.² Tumours are, by definition, environments that promote growth of neoplastic cells. Clear cell renal cell carcinoma, in particular, provides a unique pro-tumour environment, in part due to its molecular characteristics, affording metastatic tumours the opportunity to survive and grow.³ We describe a case of metastatic breast carcinoma that was found within a conventional clear cell type renal cell carcinoma. Further, this case illustrates the potential for sampling errors with percutaneous biopsies of renal masses and highlights the need for pathologists to consider the rare possibility of tumour-to-tumour metastasis when confronted with tumours showing striking morphologic heterogeneity.     

Chromophobe renal cell carcinoma: a comparative study of histological, immunohistochemical and ultrastructural features using high throughput tissue microarray

AIMS: In some cases distinction between chromophobe renal cell carcinoma (CRCC), oncocytoma and clear cell (conventional) renal cell carcinoma (eosinophilic variant) using routine light microscopy remains problematic. The present study investigates the level of agreement in the diagnosis of CRCC, as well as the histological features most frequently used for this diagnosis by two pathologists with a special interest in renal neoplasia. The sensitivity and specificity of immunohistochemical markers in cases with overlapping histological features in the diagnosis of CRCC were also studied. Electron microscopy was performed, as a diagnostic gold standard, on all of the cases. METHODS AND RESULTS: Thirty-two renal tumours with predominantly eosinophilic cytoplasm were reviewed in a blinded fashion by two pathologists. The diagnosis and morphological features used to render each diagnosis were tabulated. Validation of the utility of keratin 7 and 20, epithelial membrane antigen (EMA), vimentin, CD10, parvalbumin, RCC antigen, antimitochondrial antibody and Hale's colloidal iron was performed by the construction of a tissue microarray (TMA) master block. Based on histological criteria alone, overall agreement on the diagnosis of these tumours was reached in 69% of the cases, while there was total disagreement in 12%. In 59% of the cases, total agreement was reached in classifying the case as a CRCC based on histology alone. Kappa statistics for interobserver variability were calculated as only slight agreement (kappa = 0.3). The histological features most frequently associated with a diagnosis of CRCC were accentuated cell borders (87%) and a combination of hyperchromatic wrinkled nuclei (79%) and perinuclear halos (74%). The most sensitive and specific marker for CRCC was parvalbumin (sensitivity 0.91; specificity 1.0). The immunohistochemical profile of EMA+/ vimentin- was useful but had low specificity (sensitivity 0.75; specificity 0.4). CD10 had the highest sensitivity (1.0) but worst specificity (0.25) for CRCC. Keratin 7 had high sensitivity (0.83) but fairly low specificity (0.37) for CRCC. Hale's colloidal iron and the RCC antigen marker were not contributory. Finally, the antimitochondrial antibody was found to be fairly sensitive (0.83) for excluding CRCC. CONCLUSIONS: A small but significant proportion of renal tumours with cells having eosinophilic cytoplasm cannot be classified, even by experienced pathologists, based on histology alone. In these cases it is imperative to use markers with known sensitivity and specificity for the diagnosis of CRCC.