Small renal masses (≤ 4 cm): differentiation of oncocytoma from renal clear cell carcinoma using ratio of lesion to cortex attenuation and aorta-lesion attenuation difference (ALAD) on contrast-enhanced CT

Radiol Med. 2020 Dec;125(12):1280-1287. doi: 10.1007/s11547-020-01199-7. Epub 2020 May 8.

Abstract

Purpose: 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).

Methods: 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.

Results: 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).

Conclusion: The ratio L/C attenuation in corticomedullary phase may be useful to differentiate RO from clear cell RCC.

Keywords: Kidney neoplasms; Renal clear cell carcinoma; Renal oncocytoma; Tomography.

MeSH terms

  • Adenoma, Oxyphilic / diagnostic imaging*
  • Adenoma, Oxyphilic / pathology
  • Adult
  • Aged
  • Angiomyolipoma / diagnostic imaging
  • Aorta / diagnostic imaging*
  • Carcinoma, Papillary / diagnostic imaging
  • Carcinoma, Papillary / pathology
  • Carcinoma, Renal Cell / diagnostic imaging*
  • Carcinoma, Renal Cell / pathology
  • Contrast Media
  • Diagnosis, Differential
  • Female
  • Humans
  • Kidney Cortex / diagnostic imaging*
  • Kidney Neoplasms / diagnostic imaging*
  • Kidney Neoplasms / pathology
  • Leiomyoma / diagnostic imaging
  • Male
  • Middle Aged
  • Preoperative Period
  • Radiographic Image Enhancement
  • Retrospective Studies
  • Tomography, X-Ray Computed / methods*
  • Tumor Burden

Substances

  • Contrast Media