[980] Cytogenomic Analysis Is a Useful Adjunct Diagnostic Tool for Difficult Renal Oncocytic Tumors

Amanda L Peterson, Alberto Ayala, Jae Y Ro, Steven S Shen, Luan D Truong, Federico A Monzon. The Methodist Hospital, Houston, TX

Background: The differential diagnosis of renal oncocytic neoplasms includes clear cell renal cell carcinoma (ccRCC with granular, eosinophilic or rhabdoid features), type II papillary RCC, chromophobe RCC (chRCC) and oncocytoma. In some of these tumors morphology and immunoprofile studies may not render a definitive diagnosis. An accurate diagnosis is essential for proper patient management, especially targeted therapy. Renal tumor subtypes have been shown to have specific chromosomal gains and losses. We studied the feasibility of using cytogenomic arrays as an adjunct in the diagnosis of difficult oncocytic renal tumors.
Design: We evaluated 26 archived renal neoplasms with oncocytic features using Affymetrix 250K Nsp mapping arrays. Tumors were independently reviewed by 4 genito-urinary (GU) pathologists. Cytogenomic data was interpreted based on previously reported genomic imbalances characteristic for each renal neoplasm. These findings were compared to the morphologic diagnosis of the expert panel.
Results: Classic cytogenomic patterns of renal neoplasm subtypes were identified in 92% (24/26) of the cases. All cases in which the pathologist's panel reached a diagnostic consensus (n=11) were concordant with the molecular findings. Two cases diagnosed as RCC unclassified by the panel had cytogenomic profiles consistent with ccRCC. A majority consensus was reached in 31% (n=8) of the cases with concordant molecular findings in 62% (5/8) of these cases. The remaining 27% (n=7) of cases did not have a majority consensus and represented cases for which the differential was oncocytoma, chRCC, mixed/hybrid tumor or unclassified. The majority of these cases (n=4) had cytogenomic profiles of oncocytomas. One of these cases had a profile not classic for known renal neoplasms; however the limited number of affected chromosomes suggested an oncocytoma diagnosis.
Conclusions: Cytogenomic arrays provided chromosomal profiles that allowed classification in 92% of all difficult oncocytic renal tumor cases. In cases in which expert GU pathologists could not achieve a consensus, the use of chromosomal profiles allowed for diagnostic classification in 87% and suggested a diagnosis in the rest. We conclude that cytogenomic analysis with SNP microarrays is a useful tool to aid in the diagnosis of oncocytic renal cell neoplasms that are difficult to classify morphologically. This technique is feasible and now available to resolve these difficult cases in the clinical setting.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 164, Tuesday Morning

 

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