title: Comparison of utility of tumor size and apparent diffusion coefficient for differentiation of low- and high-grade clear-cell renal cell carcinoma.
abstract: BACKGROUND
  There is a significant correlation between tumor size and tumor grade for clear-cell renal cell carcinoma (RCC) in pathology. Thus, apparent diffusion coefficient (ADC) of clear-cell RCC might be influenced by tumor size.
  
  
  OBJECTIVE
  To compare the utility of tumor size and ADC for distinguishing low-grade from high-grade clear-cell RCC.
  
  
  METHODS
  Forty-nine patients undergoing preoperative magnetic resonance imaging were retrospectively assessed. ADC values were calculated using b-value combinations of 0 and 800 s/mm(2) at 1.5 T. Two radiologists in consensus measured ADC values via small region of interest (ROI) (mean ROI area, 88.8 mm(2); range, 80-108 mm(2)) placement on an area of solid tumor on a single slice. Maximum tumor diameter was measured at the maximum tumor area. A single pathologist reviewed all pathological slides to determine the nuclear grade according to the Fuhrman classification. The utility of ADC, tumor size, and ADC/size ratio for distinguishing low-grade from high-grade tumors was assessed. Receiver-operating characteristic (ROC) analysis and regression analysis of the each index were performed. The correlation between ADC and tumor size was also investigated.
  
  
  RESULTS
  The 49 clear-cell RCC included 34 low-grade and 15 high-grade tumors. The differences of ADC, tumor size, and ADC/size ratio between high-grade and low-grade tumors were statistically significant (P <0.05). The area under the ROC curve of ADC, tumor size, and ADC/size ratio were 0.802, 0.763, and 0.804 respectively. However, using regression analysis, only ADC (P <0.05) was statistically significant index as independent risk factors for high-grade clear-cell RCC. Moreover, weak significant correlation was observed between tumor size and ADC (R(2) = 0.3865, P <0.01).
  
  
  CONCLUSIONS
  There was a weak significant correlation between tumor size and ADC value of clear-cell RCC. Using ROC and regression analysis, ADC was statistically significant index for distinguishing low-grade from high-grade clear-cell RCC more than tumor size and ADC/size ratio.
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Mitsunari
authors: M
authors: Maruyama
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan yosizako@med.shimane-u.ac.jp.
authors: Takeshi
authors: T
authors: Yoshizako
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Koji
authors: K
authors: Uchida
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Hisayoshi
authors: H
authors: Araki
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Yukihisa
authors: Y
authors: Tamaki
authors: Department of Organ Pathology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Noriyuki
authors: N
authors: Ishikawa
authors: Department of Urology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Hiroaki
authors: H
authors: Shiina
authors: Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan.
authors: Hajime
authors: H
authors: Kitagaki
mesh_terms: D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D047368:Tumor Burden
keywords: MR diffusion/perfusion; Urinary; adults; kidney