It has recently been shown by cytogenetics that there is a high incidence of chromosome 1 abnormalities in renal oncocytomas.
To confirm the cytogenetic results by fluorescence in situ hybridization (FISH) analysis.
Nine additional cytogenetic analyses were added to those reported in our recent study, with a total of 27 tumors studied, which makes it the largest series of renal oncocytomas studied to date by cytogenetics and/or FISH. We used the LSI 1p36/LSI 1q25 Dual Color Probe Set to make the analyses.
In this study, combined cytogenetics and FISH showed loss of chromosome arm 1p1 in 48% of renal oncocytomas. By FISH, deletion of 1p36.3 was observed in 59% of renal oncocytomas, whereas by cytogenetics, abnormality in chromosome 1 was seen in 32% of tumors. However, the incidence of chromosome 1 abnormalities among 9 bilateral tumors was much higher than in single tumors (88% vs 28%, respectively). Loss of only the 1p36.3 site occurred in 2 renal oncocytomas with translocation of chromosome 1, as shown by cytogenetics. Concordance between the 2 techniques, when they were used simultaneously to detect chromosome 1p1 abnormality, was 82%.
This study further confirmed our prior results demonstrating the widespread occurrence of chromosome 1 abnormalities in renal oncocytomas. Although no abnormalities in chromosome 1 in tumors with normal karyotypes were detected by FISH using the current set of probes, a much higher incidence of such abnormalities was found in bilateral tumors, suggesting that genetic alterations related to the development of renal oncocytoma reside in this region.
"Cytogenetic studies of RO revealed genetic heterogeneity of these neoplasms; three distinct subsets were identified: 1) translocation between 11q13 and other chromosomes, 2) loss of 1/1p followed by loss of chromosome Y or 14 and 3) non-recurrent or no detectable aberrations . Molecular and fluorescent in-situ hybridization (FISH) studies of ROs described partial or total loss of chromosome 1 to be the most consistently reported clonal chromosomal abnormality in RO [11-13] with a possible tumor suppressor gene expected on chromosome 1p . In contrast, ChRCC was consistently found to display multiple losses of chromosomes 1, 2, 6, 10, 17 and 21 [12,15-17]. "
[Show abstract][Hide abstract] ABSTRACT: 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.
"Chromosomal gains are rare in oncocytomas, but gains of 7, 14, 18 and 20 have been previously reported [30,31]. Gain of 9p with concurrent loss of 9q in one of these tumors suggests the presence of an isochromosome 9p, which has also been reported in oncocytomas . Gain of 12 and loss of 18 have not, to our knowledge been previously reported. "
[Show abstract][Hide abstract] ABSTRACT: Renal epithelial tumors are morphologically, biologically, and clinically heterogeneous. Different morphologic subtypes require specific management due to markedly different prognosis and response to therapy. Each common subtype has characteristic chromosomal gains and losses, including some with prognostic value. However, copy number information has not been readily accessible for clinical purposes and thus has not been routinely used in the diagnostic evaluation of these tumors. This information can be useful for classification of tumors with complex or challenging morphology. 'Virtual karyotypes' generated using SNP arrays can readily detect characteristic chromosomal lesions in paraffin embedded renal tumors and can be used to correctly categorize the common subtypes with performance characteristics that are amenable for routine clinical use.
To investigate the use of virtual karyotypes for diagnostically challenging renal epithelial tumors, we evaluated 25 archived renal neoplasms where sub-classification could not be definitively rendered based on morphology and other ancillary studies. We generated virtual karyotypes with the Affymetrix 10 K 2.0 mapping array platform and identified the presence of genomic lesions across all 22 autosomes.
In 91% of challenging cases the virtual karyotype unambiguously detected the presence or absence of chromosomal aberrations characteristic of one of the common subtypes of renal epithelial tumors, while immunohistochemistry and fluorescent in situ hybridization had no or limited utility in the diagnosis of these tumors.
These results show that virtual karyotypes generated by SNP arrays can be used as a practical ancillary study for the classification of renal epithelial tumors with complex or ambiguous morphology.
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