We investigate the use of ratio of lesion to cortex (L/C) attenuation and aorta-lesion attenuation difference (ALAD) on multiphase contrast-enhanced CT to help distinguish oncocytoma from clear cell RCC in small renal masses (diameter < 4 cm).
We retrospectively identified 76 patients that undergo CT before surgery for a suspicious small renal mass between January 2014 and December 2018 with pathological diagnosis of 21 oncocytomas (ROs), 25 clear cell RCCs, 7 chromophobe RCCs, 7 papillary RCCs, 7 multilocular cystic RCCs, 7 angiomyolipomas and 2 leiomyomas. CT attenuation values were obtained for the tumor, the normal renal cortex and the aorta, placing a circular region of interest (ROI) in the same slice by two radiologists, independently.
In the corticomedullary phase, ROs showed isodense enhancement to the renal cortex (ratio L/C 0.92 ± 0.12), while clear cell RCCs appeared hypodense to the renal cortex (ratio L/C 0.69 ± 0.20; p < 0.01) with an accuracy of 80% for diagnosing RO. In nephrographic phase, the ratio L/C attenuation was lower than the corticomedullary phase in ROs (0.78 ± 0.11) showing an early washout pattern, while the ratio L/C was similar to the corticomedullary phase in clear cell RCCs (0.69 ± 0.13; p = 0.025, with an accuracy of 65% for diagnosing RO). The ratio L/C attenuation showed considerable overlap between ROs and clear cell RCCs in the excretory phase (p = 0.27). Mean ALAD values in the nephrographic phase were 21.95 ± 16.24 for ROs and 36.96 ± 30.53 for clear cell RCCs (p = 0.049).
The ratio L/C attenuation in corticomedullary phase may be useful to differentiate RO from clear cell RCC.
La Radiologia medica. 2020 May 08 [Epub ahead of print]
Francesco Gentili, Ilaria Bronico, Umberto Maestroni, Francesco Ziglioli, Enrico Maria Silini, Sebastiano Buti, Massimo de Filippo
Section of Radiology, Unit of Surgical Sciences, Department of Medicine and Surgery, Azienda Ospedaliero-Universitaria di Parma, University of Parma, Parma, Italy. ., Section of Radiology, Unit of Surgical Sciences, Department of Medicine and Surgery, Azienda Ospedaliero-Universitaria di Parma, University of Parma, Parma, Italy., Department of Urology, Azienda Ospedaliero-Universitaria di Parma, University of Parma, Parma, Italy., Department of Biomedical, Biotechnological and Translational Sciences, Azienda Ospedaliero-Universitaria di Parma, University of Parma, Parma, Italy.