Characterization of Renal Masses in MR Reporting: Pathologic Correlation as Part of a Performance Quality Review at an Academic Center.

Abstract

Purpose: The aim of this study was to evaluate the accuracy of MR diagnosis of renal masses in clinical practice during a 7-year period through retrospective review of MRI reports with pathologic correlation as gold standard. Materials and Methods: A retrospective review was performed of MRI reports in patients who underwent contrast-enhanced renal mass protocol MR examinations prior to biopsy/surgical resection from January 2008 to May 2015. 217 renal masses were included in the study group. The leading diagnosis, differential diagnoses, and imaging descriptors from clinical MR reports were compared with pathologic diagnosis for each lesion. Results: Pathologic diagnoses included clear-cell renal cell carcinoma (ccRCC)(n=88), papillary RCC (pRCC)(n=17), chromophobe RCC (chrRCC)(n=36), AML (n=18), oncocytoma (n=35), urothelial carcinoma (n=5), atypical RCC (n=10), atypical oncocytic neoplasm (n=6) and benign/other lesions (n=2). The sensitivity/specificity of the primary MRI differential diagnosis for malignancy was 95.1%/23.6%. The sensitivity/specificity of a primary MRI diagnosis of ccRCC was 92.3%/60.3%, for pRCC 75.0%/89.3%, and for AML 44.4/98.3%. The most common MR misdiagnoses included chrRCC misdiagnosed as pRCC/ccRCC and oncocytoma misdiagnosed as ccRCC. Conclusion: MR is highly sensitive for the diagnosis of malignancy. Diagnostic performance is lower for challenging differential diagnoses, including ccRCC versus oncocytoma, and for the diagnosis of oncocytic neoplasms.