Diagnostic usefulness of fluorescent cytogenetics in differentiating chromophobe renal cell carcinoma from renal oncocytoma: a validation study combining metaphase and interphase analyses

Genomic alterations and diagnosis of renal cancer

The application of molecular profiling has made substantial impact on the classification of urogenital tumors. Therefore, the 2022 World Health Organization incorporated the concept of molecularly defined renal tumor entities into its classification, including succinate dehydrogenase-deficient renal cell carcinoma (RCC), FH-deficient RCC, TFE3-rearranged RCC, TFEB-altered RCC, ALK-rearranged RCC, ELOC-mutated RCC, and renal medullary RCC, which are characterized by SMARCB1-deficiency. This review aims to provide an overview of the most important molecular alterations in renal cancer, with a specific focus on the diagnostic value of characteristic genomic aberrations, their chromosomal localization, and associations with renal tumor subtypes. It may not yet be the time to completely shift to a molecular RCC classification, but undoubtedly, the application of molecular profiling will enhance the accuracy of renal cancer diagnosis, and ultimately guide personalized treatment strategies for patients.

Parvalbumin immunohistochemical expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney

Parvalbumin is a cytosolic calcium-binding protein expressed in the distal convoluted tubule of the renal nephron. Among epithelial renal tumors, the reactivity for parvalbumin is observed in chromophobe renal cell carcinomas and frequently in oncocytomas. On the other hand, there are no data available on parvalbumin expression in the mesenchymal tumors of the kidney. Therefore, the purpose of this study was to evaluate the expression of parvalbumin in the spectrum of PEC (perivascular epithelioid cells) lesions of the kidney. Sixty-six PEC lesions (37 classic angiomyolipomas, 10 microscopic angiomyolipomas, 7 epithelioid angiomyolipomas/pure epithelioid PEComas, 5 leiomyoma-like angiomyolipomas, 3 lipoma-like angiomyolipomas, 2 intraglomerular lesions, 1 angiomyolipoma with epithelial cysts (AMLEC), and 1 sclerosing angiomyolipoma) were immunohistochemically stained with parvalbumin. Overall, parvalbumin immunostain was found in fifty-six PEC lesions (85%) and absent in the remaining ten cases (15%). Classic angiomyolipomas were positive in almost all cases (97%). Intraglomerular lesions and AMLEC showed parvalbumin immunolabeling as well. None of the 7 epithelioid angiomyolipomas/pure epithelioid PEComas or the only sclerosing angiomyolipoma expressed parvalbumin. In conclusion, we demonstrated the immunolabeling of parvalbumin in almost all PEC lesions of the kidney, but not in the epithelioid angiomyolipoma/pure epithelioid PEComa. This finding could shed light on some biological characteristics observed in the PEC lesions such as the plasticity of their cellular component. Moreover, parvalbumin may be another useful tool in the differential diagnosis among epithelioid angiomyolipoma/pure epithelioid PEComa with other renal eosinophilic tumors, such as oncocytoma and chromophobe renal cell carcinoma.

Comprehensive Review of Numerical Chromosomal Aberrations in Chromophobe Renal Cell Carcinoma Including Its Variant Morphologies

Chromophobe renal cell carcinoma (ChRCC) accounts for 5% to 7% of all renal cell carcinomas. It was thought for many years that ChRCC exhibits a hypodiploid genome. Recent studies using advanced molecular genetics techniques have shown more complex and heterogenous pattern with frequent chromosomal gains. Historically, multiple losses of chromosomes 1, 2, 6, 10, 13, 17, and 21 have been considered a genetic hallmark of ChRCC, both for classic and eosinophilic ChRCC variants. In the last 2 decades, multiple chromosomal gains in ChRCCs have also been documented, depicting a considerably broader genetic spectrum than previously thought. Studies of rare morphologic variants including ChRCC with pigmented microcystic adenomatoid/multicystic growth, ChRCC with neuroendocrine differentiation, ChRCC with papillary architecture, and renal oncocytoma-like variants also showed variable chromosomal numerical aberrations, including multiple losses (common), gains (less common), or chromosomal changes overlapping with renal oncocytoma. Although not the focus of the review, The Cancer Genome Atlas (TCGA) data in ChRCC show TP53, PTEN, and CDKN2A to be the most mutated genes. Given the complexity of molecular genetic alterations in ChRCC, this review analyzed the existing published data, aiming to present a comprehensive up-to-date survey of the chromosomal abnormalities in classic ChRCC and its variants. The potential role of chromosomal numerical aberrations in the differential diagnostic evaluation may be limited, potentially owing to its high variability.

Chromophobe renal cell carcinoma: current and controversial issues

It has been 35 years since Professor Thoenes and his colleagues discovered chromophobe renal cell carcinoma (RCC). Since then, our knowledge about this tumour entity has changed and novel tumour entities have been discovered. The aim of this review is to discuss recent molecular findings and open questions in diagnosing chromophobe-like/oncocytic neoplasms. The broader differential diagnosis of chromophobe-like and oncocytoma-like neoplasms includes SDH-deficient renal cell carcinoma, fumarate hydratase (FH) deficient RCC, epitheloid angiomyolipoma ('oncocytoma like'), MiT family translocation RCC and the emerging entity of eosinophilic solid and cystic renal cell carcinoma. After separation of these tumours from chromophobe RCC, it becomes evident that chromophobe RCC are low malignant tumours with a 5-6% risk of metastasis. Recent next generation sequencing (NGS) and DNA methylation profiling studies have confirmed Thoenes' theory of a distal tubule derived origin of chromophobe RCC and renal oncocytomas. Comprehensive genomic analyses of chromophobe RCC have demonstrated a low somatic mutation rate and identified TP53 and PTEN as the most frequently mutated genes, whereas 'unclassified' RCC with oncocytic or chromophobe-like features can show somatic inactivating mutations of TSC2 or activating mutations of MTOR as the primary molecular alterations. For the future, it would be desirable to create a category of 'oncocytic/chromophobe RCC, NOS' with the potential of further molecular studies for identification of TSC1/2 mutations in these rare tumours.

Juxtaglomerular cell tumor: Clinicopathologic evaluation in a large series emphasizing its broad histologic spectrum

The juxtaglomerular cell tumor (JCT) is a rare renal tumor. We re-evaluated the clinicopathologic features of 21 JCTs to summarize their variable morphologies. Immunohistochemical, fluorescent in situ hybridization and periodic acid-Schiff stains were routinely performed, and four JCT cases were detected via transmission electron microscopy. The 21 JCTs involved five males and 16 females, ranging in age from 19 years to 69 years (mean, 36.9 years; median, 34 years). The tumors were composed of large, small, or spindle cells with a round, oval or polygonal shape, arranged in various growth patterns. Both necrosis (1/21) and mitosis (2/21, with 1/50HFP, 8/50HFP) was rarely appreciated. All cases were immunoreactive for renin and CD34 (21/21), and few were positive for α-SMA (13/21;11/21, focally; 2/21, diffusely,), CD117 (9/21, focally) and synaptophysin (3/21, focally). Ultrastructurally, all four cases exhibited secretory granules in varying sizes in the cytoplasm, two of which exhibited cellular junctions. Almost all cases (20/21) had a favorable prognosis, but one succumbed due to bone and hepatic metastases, which corresponds to malignant JCT. Our study demonstrates that JCTs may have atypical clinical presentations and variable histologic appearances. A familiarity with these features may contribute to a correct diagnosis.

Sporadic oncocytic tumors with features intermediate between oncocytoma and chromophobe renal cell carcinoma: comprehensive clinicopathological and genomic profiling

Morphology, clinical behavior, and genomic profiles of renal oncocytoma (RO) and its malignant counterpart chromophobe renal cell carcinoma (ChRCC) are distinctly different. However, there is a substantial group of sporadic oncocytic tumors with peculiar hybrid phenotypes as well as a perplexing degree of morphologic and immunohistochemical overlap between classic RO and ChRCC with eosinophilic cytoplasm. The aim of this study is to provide detailed characterization of these hybrid tumors.Thirty-eight sporadic oncocytic neoplasms with ambiguous morphology from two institutions were reviewed by 4 pathologists. CKIT positivity was used as a selection criterion. We correlated CK7 and S100A1 immunostaining and detailed morphologic features with cytogenetic profiles. DNA from the formalin-fixed paraffin-embedded tissues was extracted and analyzed using cytogenomic microarray analysis (CMA) to evaluate copy number alterations (CNA) and ploidy. CMA categorized cases into 3 groups: RO (N = 21), RO variant (N = 7), and ChRCC (N = 10). Cytogenetic RO had either no CNA (48%) or loss of chromosome 1p, X, or Y (52%). RO variant had additional chromosomal losses [-9q, -14 (n = 2), -13] and chromosomal gains [+1q (n = 2), +4, +7 (n = 2), +13, +19, +20, and +22]. ChRCCs were either hypodiploid with numerous monosomies (40%) or hypotetraploid with multiple relative losses (60%). RO, RO variant, and ChRCC groups differed significantly in tumor architecture (p < 0.01), stroma (p = 0.013), presence of nuclear wrinkling, perinuclear halos, and well-defined cell borders in >5% of cells (p < 0.01), focal cell clearing (p = 0.048) and CK7 expression (p < 0.02). Pathologic prediction of the cytogenetic subtype using only two categories (benign RO or malignant ChRCC) would overcall or undercall up to 40% of tumors that were ChRCC based on cytogenetics. This finding provides the rationale for an intermediate diagnostic category of the so-called hybrid tumors (hybrid oncocytic/chromophobe tumor [HOCT]). HOCT was a heterogeneous group enriched for cytogenetic RO variant. Other HOCTs have a profile of either RO or ChRCC. The genomic profile allows classification of oncocytic tumors with ambiguous morphology into RO, RO variant, and ChRCC. Several architectural and cytologic features combined with CK7 expression are significantly associated with cytogenetic RO, RO variant, or ChRCC tumors. Doubled hypodiploidy by whole-genome endoduplication is a common phenomenon in eosinophilic ChRCC.

Chromosome 17p13 deletion is associated with an aggressive tumor phenotype in clear cell renal cell carcinoma

Background

Deletions of 17p13 recurrently occur in renal cell carcinoma (RCC) but their prognostic role seems to be uncertain.

Methods

To determine prevalence, relationship with tumor phenotype, and patient prognosis, a tissue microarray containing samples from 1809 RCCs was evaluated using dual labeling fluorescence in situ hybridization (FISH) with 17p13 and chromosome 17 centromere probes.

Results

A 17p13 deletion was found in 72 of 1429 interpretable tumors. The frequency of 17p13 deletions varied greatly between RCC subtypes and was highest in chromophobe RCC (24/72; 33.3%). 17p13 deletions were also found in 35 (3.7%) of 946 clear cell RCC, 9 (4.3%) of 208 papillary RCC, 1 of 121 oncocytomas (0.8%), as well as in several rare cases of comprising 1 of 7 Xp11.2 translocation cancers, 1 of 3 collecting duct carcinomas, and 1 of 20 not otherwise specified (NOS) carcinomas. In clear cell carcinomas, 17p13 deletions revealed a strong and consistent association with higher Fuhrman, ISUP, and Thoenes grade (p < 0.0001 each), and linked to advanced tumor stage (p = 0.0168), large tumor diameter (p = 0.0004), distant metastases (p = 0.0077), cancer-specific survival (p = 0.0391), and recurrence-free survival (p = 0.0072). In multivariate analysis, 17p13 deletions showed in clear cell RCC a dependent prognostic role for established clinical-pathological parameters.

Conclusion

17p13 deletions have a dual role in RCC. They are associated with disease progression in clear cell RCC and possibly other subtypes and they are linked to the development of chromophobe RCC—a subtype with a particularly favorable prognosis.

Assessing Genomic Copy Number Alterations as Best Practice for Renal Cell Neoplasia: An Evidence-Based Review from the Cancer Genomics Consortium Workgroup

Renal cell neoplasia are heterogeneous with diverse histology, genetic alterations, and clinical behavior that are diagnosed mostly on morphologic features. The Renal Cell Neoplasia Workgroup of the Cancer Genomics Consortium systematically evaluated peer-reviewed literature on genomic studies of renal cell carcinoma (RCC), including clear cell RCC, papillary RCC, chromophobe RCC, and the translocation RCC involving TFE3, TFEB and MITF rearrangements, as well as benign oncocytoma, which together comprise about 95% of all renal cell neoplasia. The Workgroup curated recurrent copy number alterations (CNAs), copy-neutral loss-of-heterozygosity (cnLOH), rearrangements, and mutations, found in each subtype and assigned clinical relevance according to established criteria. In clear cell RCC, loss of 3p has a disease-initiating role and most likely also in progression with mutations detected in VHL and other genes mapped to this arm, and loss of 9p and/or 14q has well-substantiated prognostic utility. Gain of chromosomes 7 and 17 are hallmark CNAs of papillary RCC, but patterns of other CNAs as detected by chromosomal microarray analysis (CMA) afford sub-classification into Type 1 and 2 with prognostic value, and for further sub-stratification of Type 2. Inherent chromosome loss in chromophobe RCC as detected by CMA is useful for distinguishing the eosinophilic variant from benign oncocytoma which in contrast exhibits few CNAs or rearranged CCND1, but share mitochondrial DNA mutations. In morphologically atypical RCCs, rearrangement of TFE3 and TFEB should be considered in the differential diagnosis, portending an aggressive RCC subtype. Overall, this evidence-based review provides a validated role for assessment of CNAs in renal cell neoplasia in the clinical setting to assist in renal cell neoplasm diagnosis and sub-classification within subtypes that is integral to the management of patients, from small incidentally found renal masses to larger surgically resected specimens, and simultaneously identify the presence of key alterations portending outcome in malignant RCC subtypes.

Combined Immunohistochemistry for the "Three 7" Markers (CK7, CD117, and Claudin-7) Is Useful in the Diagnosis of Chromophobe Renal Cell Carcinoma and for the Exclusion of Mimics: Diagnostic Experience from a Single Institution

BACKGROUND

There is a morphological overlap among renal epithelial tumors, particularly chromophobe renal cell carcinoma (CHRCC), clear cell renal cell carcinoma (CCRCC), renal oncocytoma (RO), and papillary renal cell carcinoma (PRCC). Discriminating between these tumors is important but sometimes challenging. This study is aimed at evaluating the clinical usefulness of the combined immunochemistry for the "three 7" markers (CK7, CD117, and Claudin-7) to distinguish chromophobe renal cell carcinoma from these mimics.

METHODS

Immunochemical staining for CK7, CD117, and Claudin-7 was performed in 68 CHRCCs, 199 CCRCCs, 32 ROs, and 30 PRCCs. Fluorescence in situ hybridization (FISH) was performed in some cases to exclude CCRCC and PRCC. The sensitivity (SE) and specificity (SP) for CHRCC as well as the immunoreactivity of each marker and their combinations were statistically evaluated.

RESULTS

High positive rates for CK7 (94%), CD117 (87%), Claudin-7 (94%), and their combinations (CK7+CD117, 79%; CK7+Claudin-7, 88%; CD117+Claudin-7, 82%; CK7+CD117+Claudin-7, 76%) were observed in CHRCC compared to those in CCRCC, RO, and PRCC, with increasingly higher SP when combinations of the "three 7" markers were applied (CK7, 0.80; CD117, 0.82; Claudin-7, 0.78; CK7+CD117, 0.95; CK7+Claudin-7, 0.97; CD117+Claudin-7, 0.97; CK7+CD117+Claudin-7, 1).

CONCLUSION

CK7, CD117, and Claudin-7 are frequently expressed in CHRCC with high specificity. We recommend the routine use of these 3 markers as a routine panel when making a differential diagnosis of CHRCC and excluding other mimics.

Classic Chromophobe Renal Cell Carcinoma Incur a Larger Number of Chromosomal Losses Than Seen in the Eosinophilic Subtype

Chromophobe renal cell carcinoma (chRCC) is a renal tumor subtype with a good prognosis, characterized by multiple chromosomal copy number variations (CNV). The World Health Organization (WHO) chRCC classification guidelines define a classic and an eosinophilic variant. Large cells with reticular cytoplasm and prominent cell membranes (pale cells) are characteristic for classic chRCC. Classic and eosinophilic variants were defined in 42 Swiss chRCCs, 119 Japanese chRCCs and in whole-slide digital images of 66 chRCCs from the Cancer Genome Atlas (TCGA) kidney chromophobe (KICH) dataset. 32 of 42 (76.2%) Swiss chRCCs, 90 of 119 (75.6%) Japanese chRCCs and 53 of 66 (80.3%) TCGA-KICH were classic chRCCs. There was no survival difference between eosinophilic and classic chRCC in all three cohorts. To identify a genotype/phenotype correlation, we performed a genome-wide CNV analysis using Affymetrix OncoScan^® CNV Assay (Affymetrix/Thermo Fisher Scientific, Waltham, MA, USA) in 33 Swiss chRCCs. TCGA-KICH subtypes were compared with TCGA CNV data. In the combined Swiss and TCGA-KICH cohorts, losses of chromosome 1, 2, 6, 10, 13, and 17 were significantly more frequent in classic chRCC (p < 0.05, each), suggesting that classic chRCC are characterized by higher chromosomal instability. This molecular difference justifies the definition of two chRCC variants. Absence of pale cells could be used as main histological criterion to define the eosinophilic variant of chRCC.

Chromosomal aberrations in renal cell carcinoma: An overview with implications for clinical practice

Chromosomal instability and aberrations are known in many cancers including renal cell carcinoma. Detailed understanding of these changes has led to an improved drug discovery and continued developments in other therapeutic options. Chromosomal aberrations have a potential to be used to monitor disease including prognostication. There has been a growing experience in cytogenetic techniques and gap between clinic and laboratory has narrowed significantly in the recent past. Nevertheless, more work on validation of these techniques, establishing threshold and interobserver agreement needs to be carried out for these diagnostic/prognostic tests before utilizing them in clinics as a part of “personalized medicine” care. The review presented here is a summary of common genetic disorders in renal cancer and some of acquired genetic changes which can be used as biomarkers. The review also describes basics of commonly used genetic techniques for wider clinical community involved in the management of renal cancer.

Renal cell carcinoma: the search for a reliable biomarker

One particular challenge in the treatment of kidney tumors is the range of histologies and tumor phenotypes a renal mass can represent. A kidney tumor can range from benign (e.g., oncocytoma) to a clinically indolent malignancy (e.g., papillary type I, chromophobe) to aggressive disease [e.g., papillary type II or high-grade clear cell renal cell carcinoma (ccRCC)]. Even among various subtypes, kidney cancers are genetically diverse with variable prognoses and treatment response rates. Therefore, the key to proper treatment is the differentiation of these subtypes. Currently, a wide array of diagnostic, prognostic, and predictive biomarkers exist that may help guide the individualized care of kidney cancer patients. This review will discuss the various serum, urine, imaging, and immunohistological biomarkers available in practice.

Genetic alterations of HER genes in chromophobe renal cell carcinoma

Chromophobe (ch) renal cell carcinoma (RCC) is the 3rd most common subtype of RCC and occurs in 5% of all RCCs. Although chRCC generally demonstrates more favorable outcomes compared with other subtypes of RCC, there is a 6-7% probability of tumor progression and metastasis in this disease. The subclassification of a more aggressive subtype of chRCC may be useful for the management of this cancer. The Erb-B2 receptor tyrosine kinase 2 [also known as human epidermal growth factor receptor (HER) 2] gene has been reported to be important in chRCC. The present study aimed to further investigate the abnormalities of the HER family genes and their potential association with chRCC. Fluorescence in situ hybridization was performed on 11 chRCC tissue specimens, and the Spearman's rank correlation coefficient analysis was used to assess the results. The loss of one copy of the HER2 and HER4 genes was observed to be the major alteration of the tumor cells in all chRCC cases. Statistical data indicated that loss of the HER2 gene was strongly correlated with loss of the HER4 gene (P=0.019). The findings of previous studies were also combined for analysis, and were consistent with those of the present study. In addition, the amplification of HER1 was also strongly correlated with the amplification of HER4 (P=0.004). Furthermore, a high percentage of genetic structural rearrangements was observed in HER3 genes, which was significantly associated with amplification of HER2 (P=0.005). Certain alterations in the HER gene family were also noted as a phenomenom in chRCC. Therefore, the characterization of the underlying aberrant functions of HER genes may be of interest for additional studies in the context of using HER genes to distinguish between RCC subtypes in order to establish improved treatment guidelines.

Magnetic Resonance Imaging as a Biomarker for Renal Cell Carcinoma

As the most common neoplasm arising from the kidney, renal cell carcinoma (RCC) continues to have a significant impact on global health. Conventional cross-sectional imaging has always served an important role in the staging of RCC. However, with recent advances in imaging techniques and postprocessing analysis, magnetic resonance imaging (MRI) now has the capability to function as a diagnostic, therapeutic, and prognostic biomarker for RCC. For this narrative literature review, a PubMed search was conducted to collect the most relevant and impactful studies from our perspectives as urologic oncologists, radiologists, and computational imaging specialists. We seek to cover advanced MR imaging and image analysis techniques that may improve the management of patients with small renal mass or metastatic renal cell carcinoma.

Genetic and Chromosomal Aberrations and Their Clinical Significance in Renal Neoplasms

The most common form of malignant renal neoplasms is renal cell carcinoma (RCC), which is classified into several different subtypes based on the histomorphological features. However, overlaps in these characteristics may present difficulties in the accurate diagnosis of these subtypes, which have different clinical outcomes. Genomic and molecular studies have revealed unique genetic aberrations in each subtype. Knowledge of these genetic changes in hereditary and sporadic renal neoplasms has given an insight into the various proteins and signalling pathways involved in tumour formation and progression. In this review, the genetic aberrations characteristic to each renal neoplasm subtype are evaluated along with the associated protein products and affected pathways. The potential applications of these genetic aberrations and proteins as diagnostic tools, prognostic markers, or therapeutic targets are also assessed.

Expression of histone methyltransferases as novel biomarkers for renal cell tumor diagnosis and prognostication

Renal cell tumors (RCTs) are the most lethal of the common urological cancers. The widespread use of imaging entailed an increased detection of small renal masses, emphasizing the need for accurate distinction between benign and malignant RCTs, which is critical for adequate therapeutic management. Histone methylation has been implicated in renal tumorigenesis, but its potential clinical value as RCT biomarker remains mostly unexplored. Hence, the main goal of this study was to identify differentially expressed histone methyltransferases (HMTs) and histone demethylases (HDMs) that might prove useful for RCT diagnosis and prognostication, emphasizing the discrimination between oncocytoma (a benign tumor) and renal cell carcinoma (RCC), especially the chromophobe subtype (chRCC). We found that the expression levels of 3 genes--SMYD2, SETD3, and NO66--was significantly altered in a set of RCTs, which was further validated in a large independent cohort. Higher expression levels were found in RCTs compared to normal renal tissues (RNTs) and in chRCCs comparatively to oncocytomas. SMYD2 and SETD3 mRNA levels correlated with protein expression assessed by immunohistochemistry. SMYD2 transcript levels discriminated RCTs from RNT, with 82.1% sensitivity and 100% specificity [area under curve (AUC) = 0.959], and distinguished chRCCs from oncocytomas, with 71.0% sensitivity and 73.3% specificity (AUC = 0.784). Low expression levels of SMYD2, SETD3, and NO66 were significantly associated with shorter disease-specific and disease-free survival, especially in patients with non-organ confined tumors. We conclude that expression of selected HMTs and HDMs might constitute novel biomarkers to assist in RCT diagnosis and assessment of tumor aggressiveness.

Renal tumors: diagnostic and prognostic biomarkers

The International Society of Urological Pathology convened a consensus conference on renal cancer, preceded by an online survey, to address issues relating to the diagnosis and reporting of renal neoplasia. In this report, the role of biomarkers in the diagnosis and assessment of prognosis of renal tumors is addressed. In particular we focused upon the use of immunohistochemical markers and the approach to specific differential diagnostic scenarios. We enquired whether cytogenetic and molecular tools were applied in practice and asked for views on the perceived prognostic role of biomarkers. Both the survey and conference voting results demonstrated a high degree of consensus in participants' responses regarding prognostic/predictive markers and molecular techniques, whereas it was apparent that biomarkers for these purposes remained outside the diagnostic realm pending clinical validation. Although no individual antibody or panel of antibodies reached consensus for classifying renal tumors, or for confirming renal metastatic disease, it was noted from the online survey that 87% of respondents used immunohistochemistry to subtype renal tumors sometimes or occasionally, and a majority (87%) used immunohistochemical markers (Pax 2 or Pax 8, renal cell carcinoma [RCC] marker, panel of pan-CK, CK7, vimentin, and CD10) in confirming the diagnosis of metastatic RCC. There was consensus that immunohistochemistry should be used for histologic subtyping and applied before reaching a diagnosis of unclassified RCC. At the conference, there was consensus that TFE3 and TFEB analysis ought to be requested when RCC was diagnosed in a young patient or when histologic appearances were suggestive of the translocation subtype; whereas Pax 2 and/or Pax 8 were considered to be the most useful markers in the diagnosis of a renal primary.

Differentiation of oncocytoma from chromophobe renal cell carcinoma (RCC): can novel molecular biomarkers help solve an old problem?

Standard treatment of renal neoplasms remains surgical resection, and nephrectomy for localised renal cell carcinoma (RCC) still has the best chance of cure with excellent long-term results. For smaller renal masses, especially stage T1a tumours less than 4 cm, nephron-sparing surgery is often employed. However, small incidentally detected renal masses pose an important diagnostic dilemma as a proportion of them may be benign and could be managed conservatively. Renal oncocytoma is one such lesion that may pose little risk to a patient if managed with routine surveillance rather than surgery. Additionally, lower-risk RCC, such as small chromophobe RCC, may be managed in a similar way, although with more caution than the renal oncocytomas (RO). The ability to differentiate ROs from chromophobe RCCs, and from other RCCs with a greater chance of metastasis, would guide the physician and patient towards the most appropriate management, whether nephron-sparing surgical resection or conservative surveillance. Consistent accurate diagnosis of ROs is likely to remain elusive until modern molecular biomarkers are identified and applied routinely. This review focuses on the differentiation of renal oncocytomas and chromophobe RCCs. It summarises the history, epidemiology and clinical presentation of the renal neoplasms, explains the diagnostic dilemma, and describes the value, or not, of current molecular markers that are in development to assist in diagnosis of the renal neoplasms.

Chromophobe renal cell carcinoma--chromosomal aberration variability and its relation to Paner grading system: an array CGH and FISH analysis of 37 cases

Genetically, chromophobe renal cell carcinoma (ChRCC) is characterized by multiple chromosomal changes, especially losses. The most common losses include chromosomes 1, 2, 6, 10, 13, 17, and 21. The Fuhrman grading system lacks prognostic relevance for ChRCC, and recently, a new grading system for ChRCC was proposed by Paner. The objective of this study was to map the spectrum of chromosomal aberrations (extent and location) in a large cohort of ChRCCs and relate these findings to the Paner grading system (PGS). A large cohort of ChRCC was reviewed and graded according to the PGS. All the cases were reevaluated and separated into groups according to their PGS. The final study set was 37 patients. ChRCCs were divided into PG 1-3, sarcomatoid, and aggressive groups. "Aggressive ChRCCs" were designated cases with known metastatic activity, local recurrence, aggressive growth to the adjacent organs, or invasive growth into the renal sinus (with/without angioinvasion). Sarcomatoid tumors were divided into their epithelial and sarcomatoid component (further molecular genetic analyses were performed separately). Array comparative genome hybridization and/or fluorescence in situ hybridization analysis was applied to 42 samples from the 37 cases. Multiple losses, as well as gains, were detected in different chromosomes. Regardless of the PGS groups, the most frequently detected losses involved chromosomes 1 (27/37), 2 (26/37), 6 (23/37), 10 (26/37), 13 (19/37), and 17 (24/37). Loss of chromosome 21 was found in 12/37 cases. The most frequently detected gains were found on chromosomes 4 (22/37), 7 (24/37), 15 (20/37), 19 (22/37), and 20 (21/37). Cluster analysis showed that there is no relation between PGS and particular pattern of chromosomal changes (losses or gains) in ChRCCs. Conclusions are as follows: (1) ChRCCs showed a significantly broader spectrum of chromosomal aberrations than previously recognized. While previously published chromosomal losses were found in our cohort, gains of multiple chromosomes were also identified in a high percentage. The most frequently detected gains involved chromosomes 4, 7, 15, 19, and 20. (2) There is no relation between chromosomal numerical changes and Paner grading system.

Potential role of genetic markers in the management of kidney cancer

CONTEXT

Kidney cancer is not a single entity but comprises a number of different types of cancer that occur in the kidney including renal cell tumours as the most common type. Four major renal cell tumour subtypes can be distinguished based on morphologic and genetic characteristics. To individualise therapy and to improve the prognosis in patients with renal cell tumours, accurate subtyping, definition of individual course of disease, and the prediction of therapy response are necessary.

OBJECTIVE

To discuss the potential role of genetic markers in the management of kidney cancer.

EVIDENCE ACQUISITION

A Medline search was conducted to identify original articles, review articles, and editorials addressing the role of genetic alterations in kidney cancer management. Keywords included kidney neoplasms, genetics, SNP, gene expression, miRNA, classification, diagnosis, drug therapy, prognosis, and therapy. The articles with the highest level of evidence were identified and critically reviewed. This review is the result of an interactive peer-reviewing process by an expert panel of co-authors.

EVIDENCE SYNTHESIS

Each subtype is characterised by specific genetic, epigenetic, and expression patterns that potentially can be used to subclassify renal cell tumours in cases of ambivalent histopathology. Molecular signatures and single alterations in primary tumours are associated with aggressiveness and prognosis. Germline polymorphisms in specific genes encoding for metabolizing enzymes, efflux transporters, and drug targets seem to be associated with toxicity and response in patients receiving targeted therapy.

CONCLUSIONS

Significant advances have been achieved in the molecular analysis of renal cancer. Validation of findings is greatly needed to implement genetic markers in the management of renal cancer. This should lead to improved diagnosis, prognosis, and personalised therapy in this heterogeneous disease.

Mitochondria with tubulovesicular cristae in renal oncocytomas

Renal oncocytoma and chromophobe renal cell carcinoma (CRCC) are closely related tumors. They are considered the extremes of a spectrum with several variants. Ultrastructural examination of the mitochondria is a helpful procedure in the diagnosis of these neoplasms. Renal oncocytomas show mitochondria with piled lamellar cristae, and CRCC exhibited mitochondria with tubulovesicular cristae. In a series of 23 histologically diagnosed renal oncocytomas examined by electron microscopy, the authors found 5 tumors exhibiting more cells with mitochondria showing tubulovesicular cristae. The authors believe these 5 cases present a submicroscopic appearance intermediate between renal oncocytoma and CRCC, although with benign clinical behavior.