Lack of genetic changes at specific genomic sites separates renal oncocytomas from renal cell carcinomas

Oncocytic variant, a novel subtype of chromophobe renal cell carcinoma: a report of two cases and a literature review

A novel variant of chromophobe renal cell carcinoma showing an oncocytic phenotype is proposed. Two new cases of this rare entity are presented and discussed along with six previous cases from our colleagues. A 76-year-old man and a 78-year-old man had a 3.4-cm and a 3.2-cm-diameter renal mass, respectively. On histopathological examination of surgical specimens, uniform eosinophilic cuboidal cells without a perinuclear halo growing in a tubular pattern were seen, and differential diagnosis from oncocytoma was necessary. Immunohistochemical staining for cytokeratin 7 and E-cadherin showed diffusely positive patterns in both, as in the previous reports. Although monosomy of chromosomes 7, 10, 13, and 17 was commonly observed in the previous reports, gains of chromosome 19 were observed in the two present cases. Immunohistochemical and cytogenetic approaches lead to exclusion of oncocytoma and the diagnosis of an oncocytic variant of chromophobe renal cell carcinoma.

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.

Molecular pathology of renal oncocytoma: a review

Differentiating renal oncocytoma from its renal cell carcinoma (RCC) mimics, particularly chromophobe RCC, can be difficult, especially when limited tissue is available for evaluation and requires sophisticated microscopic, ultrastructural and immunohistochemical evaluation. In this review, the relevant literature has been reviewed, and supporting data obtained by applying modern microarray-based technologies are discussed with a focus on molecular pathology of renal oncocytoma. The high resolution whole-genome DNA-microarray based analyses excluded with all certainty the occurrence of small specific alterations. Renal oncocytomas are characterized by variable chromosomal patterns. The number of genes selected by global gene expression analyses and their usefulness in the diagnostic pathology based on immunohistochemical evaluation is far below the expectations. The conflicting staining patterns, together with the poor specificity of proposed antibodies, leads us to believe that these candidate immunomarkers might not help in the separation of these tumors. Applying DNA based tools might help in the diagnosis of renal oncocytoma with uncertain histology. However, only the combination of all available techniques could give reliable information.

Molecular pathology of chromophobe renal cell carcinoma: a review

The recognition of chromophobe renal cell carcinoma (RCC) among other distinct types of renal cell tumors (RCT) based on light-microscopic features, such as cytoplasmic and nuclear characteristics, might pose a dilemma in some cases because of morphological pattern overlapping with renal oncocytoma or conventional RCC. The present article reviews chromophobe RCC with focus on aspects of its molecular pathology, which was shown using ancillary modern microarray-based technology that can distinguish it from its mimics and therefore be helpful for its correct diagnosis. Although the high resolution DNA-microarray analyses excluded with all certainty the occurrence of small specific alterations, the loss of entire chromosomes 2, 10, 13, 17 and 21 occurs exclusively in chromophobe RCC and therefore probes localized at these chromosomes might be used to establish the diagnosis of chromophobe RCC in cases with uncertain histology. The usefulness of proposed candidate genes selected by the global gene expression analyses in the diagnostic pathology is far below expectations. The conflicting staining patterns, together with the poor specificity of used antibodies, leads us to believe that these candidate immunomarkers might not help in the separation of chromophobe RCC, with the exception of CD82, which has recently been suggested to be used for routine histological diagnosis.

Renal oncocytoma: a comparative clinicopathologic study and fluorescent in-situ hybridization analysis of 73 cases with long-term follow-up

Clinical studies have confirmed that renal oncocytoma (RO) is a benign neoplasm with excellent prognosis. In diagnostically challenging cases of renal oncocytic epithelial neoplasms, fluorescent in-situ hybridization (FISH) is increasingly being used and its ability to distinguish RO from chromophobe renal cell carcinoma (ChRCC) has been documented. In this study, we evaluated the differential diagnostic contribution of FISH in cases of RO.

Clinicopathologic data and glass slides from 73 patients with RO were reviewed; 20 cases of ChRCC were included for comparison. FISH analysis of formalin-fixed, paraffin-embedded sections was performed using centromeric probes for chromosomes 1, 2, 7 and 17. FISH analysis revealed ROs had frequent loss of signal for chromosome 1 (56%) and 17 (44%). Tumors with more than one loss were common (41%) and 10% cases showed loss of all chromosomes examined. A total of 18% cases did not show any abnormality.

Our study shows that chromosomal abnormalities in both ROs and ChRCCs are common with frequent loss of chromosomes 1 and 17. No association was found between overall patient survival and the extent of chromosomal abnormalities. FISH results, even those showing significant chromosomal abnormalities, should not alter the primarily morphology-based diagnosis of RO.

Sporadic hybrid oncocytic/chromophobe tumor of the kidney: a clinicopathologic, histomorphologic, immunohistochemical, ultrastructural, and molecular cytogenetic study of 14 cases

Hybrid oncocytic/chromophobe tumors (HOCT) of the kidney have been described in patients with Birt-Hogg-Dubé syndrome (BHD) and in association with renal oncocytosis without BHD. HOCT in patients without evidence of BHD or renal oncocytosis is exceedingly rare, and these cases have been poorly characterized. We have identified and studied 14 cases of HOCT from previously diagnosed renal oncocytomas (398 cases) and chromophobe renal cell carcinomas (351 cases) without evidence of BHD or renal oncocytosis. Immunohistochemical, ultrastructural, and molecular genetic studies analyzing numerical chromosomal changes, loss of heterozygosity for chromosome 3p, and mutation status of VHL, c-kit, PDGFR, and folliculin (FLCN) genes were performed. HOCTs were identified in nine men and five women (age range 40-79 years). The size of tumors ranged from 2 to 11 cm. All tumors displayed a solid alveolar architecture and were composed of cells with abundant granular eosinophilic oncocytic cytoplasm with perinuclear halos. Occasional binucleated neoplastic cells were present, but irregular, hyperchromatic, wrinkled (raisinoid) nuclei were absent. The cytoplasm contained numerous mitochondria of varying sizes, but only sparse microvesicles with amorphic lamellar content were found. Tumors were positive for CK7 (12/14), AE1-AE3 (14/14), anti-mitochondrial antigen (14/14), E-cadherin (11/13), parvalbumin (12/14), and epithelial membrane antigen (14/14). Tumors were generally negative for racemase, CK20, CD10, and carboanhydrase IX. Interphase fluorescence in situ hybridization revealed multiple chromosomal losses and gains with a median of four (range 1-9) chromosomal aberrations per case. Monosomy of chromosome 20 was common and found in 7 of 14 cases. Monosomy of chromosomes 6 and 9 was present in 4 of 14 cases each, of which two cases displayed monosomy for both chromosomes 6 and 9. Polysomy of chromosomes 10, 21, and 22 was found in 4/14 cases each, of which one case displayed polysomy for all these three chromosomes. No pathogenic mutations were found in the VHL, c-kit, PDGFR, and folliculin (FLCN) genes. (1) We have shown that hybrid oncocytic/chromophobe tumors of the kidney do occur, albeit rarely, outside the Birt-Hogg-Dubé syndrome and without associated renal oncocytosis. (2) These tumors constitute a relatively homogenous group with histomorphologic features of both chromophobe renal cell carcinoma and renal oncocytoma. (3) Sporadic hybrid oncocytic/chromophobe renal tumors are characterized by multiple numerical aberrations (both mono- and polysomies) of chromosomes 1, 2, 6, 9, 10, 13, 17, 21, and 22 and lack of mutations in the VHL, c-kit, PDGFRA, and FLCN genes. (4) The tumors seem to behave indolently as no evidence of malignant behavior was documented in our series, although admittedly, the follow-up was too short to fully elucidate the biological nature of this rare neoplasm. At worst, these tumors could have a low malignant potential, which only can be found out with longer follow-up.

Genetic profiles in renal tumors

Renal cell carcinoma in adult comprises a heterogeneous group of tumors with variable clinical outcomes, which ranges from indolent to aggressively malignant. The application of molecular genetics techniques to the study of renal neoplasms has resulted in improved classification of these entities and better understanding of biological mechanisms responsible for tumor development and progression. In the present article we review the molecular genetic profiles of different renal cell tumors and discuss their relevance to the carcinogenesis mechanisms and to the clinical diagnosis of renal cell carcinoma. Understanding of the molecular genetics of renal tumors is beneficial in making accurate diagnoses, assessing prognoses, and selecting appropriate and targeted therapeutic options.

High-resolution DNA copy number and gene expression analyses distinguish chromophobe renal cell carcinomas and renal oncocytomas

Background

The diagnosis of benign renal oncocytomas (RO) and chromophobe renal cell carcinomas (RCC) based on their morphology remains uncertain in several cases.

Methods

We have applied Affymetrix GeneChip Mapping 250 K NspI high-density oligoarrays to identify small genomic alterations, which may occur beyond the specific losses of entire chromosomes, and also Affymetrix GeneChip HG-U133 Plus2.0 oligoarrays for gene expression profiling.

Results

By analysing of DNA extracted from 30 chRCCs and 42 ROs, we have confirmed the high specificity of monosomies of chromosomes 1, 2, 6, 10, 13, 17 and 21 in 70–93% of the chRCCs, while ROs displayed loss of chromosome 1 and 14 in 24% and 5% of the cases, respectively. We demonstrated that chromosomal gene expression biases might correlate with chromosomal abnormalities found in chromophobe RCCs and ROs. The vast majority genes downregulated in chromophobe RCC were mapped to chromosomes 2, 6, 10, 13 and 17. However, most of the genes overexpressed in chromophobe RCCs were located to chromosomes without any copy number changes indicating a transcriptional regulation as a main event.

Conclusion

The SNP-array analysis failed to detect recurrent small deletions, which may mark loci of genes involved in the tumor development. However, we have identified loss of chromosome 2, 10, 13, 17 and 21 as discriminating alteration between chromophobe RCCs and ROs. Therefore, detection of these chromosomal changes can be used for the accurate diagnosis in routine histology.

Differential expression of a new isoform of DLG2 in renal oncocytoma

Background

Renal oncocytoma, a benign tumour of the kidney, may pose a differential diagnostic problem due to overlapping phenotype with chromophobe renal cell carcinoma or other types of renal cell tumours. Therefore, identification of molecular markers would be of great value for molecular diagnostics of this tumour type.

Methods

In the current study we applied various techniques, including Affymetrix microarray hybridization and semiquantitative RT-PCR, to identify genes expressed differentially in renal oncocytomas. Subsequently, we used RACE and Northern blot hybridization to characterize the potential candidates for molecular diagnosis.

Results

We have identified new isoform of DLG2 gene, which contains 3'-end exons of the known DLG2 gene along with the hypothetical gene FLJ37266. The new isoform is specifically upregulated in renal oncocytoma, whereas the known DLG2 gene is downregulated in this type of kidney tumour.

Conclusion

The new isoform of DLG2 is the promising candidate gene for molecular differential diagnostics of renal oncocytoma.

Application of molecular diagnostic techniques to renal epithelial neoplasms

The application of molecular and cytogenetic techniques to the study of renal neoplasia has resulted in improved understanding of the biologic mechanisms that are responsible for tumor development and progression. It also revealed that several different and specific genetic events are responsible for tumorigenesis in the various categories and subcategories of renal tumors. The ultimate goal of research on the molecular pathology of renal neoplasms is a complete understanding of the genetics of these tumors, which will, in turn, aid in making the correct diagnosis, accurately assessing prognosis, and selecting appropriate and targeted therapeutic options.

Eosinophilic and classic chromophobe renal cell carcinomas have similar frequent losses of multiple chromosomes from among chromosomes 1, 2, 6, 10, and 17, and this pattern of genetic abnormality is not present in renal oncocytoma

That chromophobe renal cell carcinoma has an uncommon eosinophilic variant has been recognized for more than a decade. In sections stained with hematoxylin and eosin, the eosinophilic variant of chromophobe renal cell carcinoma and renal oncocytoma are similar in appearance. While it is well established that chromophobe renal cell carcinoma and renal oncocytoma have different patterns of genetic anomalies, little is known of the genetics of the eosinophilic variant of chromophobe renal cell carcinoma. This study was undertaken to elucidate the genetic lesions of eosinophilic chromophobe renal cell carcinoma and to compare them with those found in classic chromophobe renal cell carcinoma and in renal oncocytoma. A total of 29 renal neoplasms--nine eosinophilic chromophobe renal cell carcinomas, 10 classic chromophobe renal cell carcinomas, and 10 oncocytomas--were investigated by fluorescence in situ hybridization on 5 microm paraffin-embedded tissue sections with centromeric probes for chromosomes 1, 2, 6, 10, and 17. Signals were counted in 100-200 neoplastic nuclei from each tumor. Chromophobe renal cell carcinomas frequently showed loss of chromosomes 1 (70% of classic, 67% of eosinophilic), 2 (90% classic, 56% eosinophilic), 6 (80% classic, 56% eosinophilic), 10 (60% classic, 44% eosinophilic), and 17 (90% classic, 78% eosinophilic); Among the classic chromophobe renal cell carcinomas, only one had no loss of any of the chromosomes, while 50% had loss of all five chromosomes. Among the eosinophilic chromophobe renal cell carcinomas, one of nine had no loss and 44% had loss of all five chromosomes. One oncocytoma had loss of chromosome 1. No other chromosomal loss was detected in the oncocytomas. In conclusion, losses of chromosomes 1, 2, 6, 10, and 17 are frequent in both eosinophilic and classic chromophobe renal cell carcinomas. Loss of chromosome 1 occurs occasionally in oncocytoma but losses of chromosomes 2, 6, 10, and 17 are not found in oncocytomas. When the differential diagnostic problem is oncocytoma vs eosinophilic chromophobe renal cell carcinoma, detection of losses of chromosomes 2, 6, 10, or 17 effectively excludes the diagnosis of oncocytoma and supports the diagnosis of chromophobe renal cell carcinoma.

The genetics of renal oncocytosis: a possible modelfor neoplastic progression

Renal oncocytosis is a rare condition characterized by the presence of numerous oncocytomas and oncocytic changes in the renal tubules. Other than oncocytomas associated with the Birt-Hogg-Dube (BDH) syndrome, the genetics of oncocytosis is not known. Whether oncocytomas and oncocytosis are similar to BDH syndrome, in which the tumors diploid (as most oncocytomas are), or show chromosomal losses may be significant regarding the observation that in oncocytosis, there frequently is morphological evidence of progression to chromophobe carcinoma. Here we report on the case of a 69-year old male who underwent a staged procedure of partial nephrectomy on the left side and right radical nephrectomy for multiple renal tumors. The tumors were studied by routine hematoxylin and eosin morphology, immunohistochemistry, cytogenetics, and loss of heterozygosity analysis. Both kidneys had numerous oncocytic neoplasms morphologically progressing from oncocytomas to hybrid tumors with chromophobe carcinoma. Genetic studies demonstrated progression from normal cytogenetics to chromosomal losses similar to those in some oncocytomas and in chromophobe carcinomas. The genetics of this apparently nonfamilial oncocytoma differs from that of BDH syndrome and is characterized by losses involving chromosomes 1, 14, 21, and Y. To our knowledge, this is the first report of the genetic and cytogenetic findings in oncocytosis not related to BDH syndrome and may suggest a possible model of progression from oncocytoma to chromophobe renal cell carcinoma.

Microsatellite allelotyping differentiates chromophobe renal cell carcinomas from renal oncocytomas and identifies new genetic changes

AIMS

The diagnosis of renal oncocytomas (ROs) and chromophobe renal cell carcinomas (RCCs) based on histological features is often uncertain. To assess the value of genetic analysis in their differential diagnosis we analysed 27 ROs and 21 chromophobe RCCs by microsatellite allelotyping.

METHODS AND RESULTS

Markers at the short and long arms of chromosomes specifically involved in the genetic changes of the four main types of renal cancers were selected. Allelic changes were identified by automated sequencing. Allelic changes at chromosome 1p occurred in 8/26 (31%) and at chromosome 14q in 4/27 (15%) ROs. Loss of heterozygosity (LOH) at chromosomes 1, 2, 6, 10, 13, 17 and 21 were seen in 90%, 90%, 96%, 86%, 85%, 90% and 72% of the chromophobe RCCs, respectively. Alterations of at least three of these chromosomal sites were detected in each chromophobe RCC. In addition, we found recurrent LOH at chromosomes 9p23 (43%), 18q22 (30%), 5q22 (28%) and 8p (28%) in chromophobe RCCs.

CONCLUSIONS

Chromophobe RCCs can be differentiated from ROs by analysing specific chromosomal regions with microsatellites.

Identifying BAC clones for diagnosis of conventional renal cell carcinoma by FISH

AIMS

The new classification of renal cell tumours relies on tumour-specific genetic alterations, which can be detected by different techniques. For diagnosis of conventional renal cell carcinoma by FISH we have isolated BAC clones from the chromosomal regions of interest.

METHODS AND RESULTS

A BAC library was screened by microsatellites mapped to the smallest overlapping regions of loss of heterozygosity (LOH) at chromosomes 3p, 5q, 6q, 8p, 9p and 14q. Positive BACs were tested by carrying out FISH in normal cells for signal/noise ratio. Subsequently, 11 conventional and two papillary renal cell carcinomas were analysed by the new diagnostic BAC set and the results were compared with those obtained by microsatellite allelotyping. The diagnostic value of FISH was comparable to that of microsatellite analysis in nearly all tumours except those with extreme chromosomal polyploidization.

CONCLUSIONS

We conclude that both FISH and microsatellite analyses are helpful to strengthen the diagnosis of conventional renal cell carcinoma. However, both techniques may have some disadvantage in a special setting.

Small cell variant of renal oncocytoma--a rare and misleading type of benign renal tumor

Here we report 3 cases of renal oncocytoma with a dominating small cell component arising in adult women. These 3 cases of small cell variant of renal oncocytoma were found among 134 cases of oncocytomas of the kidney in the routine and consultation files of the authors. Two of 3 cases were initially thought to be a malignant tumor by the referring pathologists. In all 3 cases minor areas of the tumors, which were identical to the classical renal oncocytomas were found. The small cell areas were arranged in a characteristic organoid pattern different from all the known types of the renal benign and malignant tumors. We summarize all morphologic, immunohistochemical, and ultrastructural features of this unusual oncocytoma variant with regard to its differential diagnosis. Int J Surg Pathol 9(3):215-222, 2001

Lack of interleukin 6 (IL-6) and transforming growth factor alpha (TGF-alpha) expression in chromophobe renal cell carcinomas

We demonstrate the constitutive expression of interleukin 6 (IL-6), IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) in normal kidney cells, and in the majority of renal oncocytomas, papillary and non-papillary renal cell carcinomas (RCCs) by reverse transcriptase polymerase chain reaction (RT-PCR) technique. No expression of IL-6 and TGF-alpha and variable expression of GM-CSF, IL-8, EGF and EGFR was seen in chromophobe RCCs. The lack of expression of IL-6 and TGF-alpha might be correlated with the growth pattern, poor vascularity and low malignancy of chromophobe RCCs.