title: Triphasic and epithelioid minimal fat renal angiomyolipoma and clear cell renal cell carcinoma: qualitative and quantitative CEUS characteristics and distinguishing features.
abstract: OBJECTIVE
  To determine the contrast-enhanced ultrasonography (CEUS) characteristics of minimal fat renal angiomyolipoma (AML) (triphasic and epithelioid) and compare them to each other and to clear cell renal cell carcinoma (ccRCC) to explore their differential diagnostic clue.
  
  
  METHODS
  Qualitative and quantitative CEUS analyses were retrospectively conducted for epithelioid renal AMLs (EAMLs) (n = 15), triphasic minimal fat AMLs (TAMLs) (n = 25), and ccRCCs (n = 113). Enhancement patterns and features with CEUS were qualitatively evaluated. As for the quantitative parameters, rise times (RT), time to peak (TTP), and tumor-to-cortex enhancement ratio (TOC ratio) were compared among these renal tumor histotypes.
  
  
  RESULTS
  No significant differences were detected on conventional ultrasound in the three histotypes of renal tumor. On qualitative CEUS analysis, centripetal enhancement in cortical phase (73.3% in EAMLs, 84.0% in TAMLs vs. 18.6% in ccRCCs, p < 0.001 for both), homogeneous peak enhancement (100.0% in both EAMLs and TAMLs vs. 43.4% in ccRCCs, p < 0.001 for both), and iso-enhancement in parenchyma phase (53.3% in AMLs, 52.0% in TAMLs vs. 26.5% in ccRCCs, p = 0.034 and 0.013, respectively) were valuable traits for differentiating EAMLs and TAMLs from ccRCCs. Furthermore, with quantitative analysis, RT and TTP were much shorter in ccRCCs than those in EAMLs and TAMLs. However, all these qualitative and quantitative characteristics made no significant difference between EAMLs and TAMLs. In the differential diagnosis of EAMLs from TAMLs, pseudocapsule sign was valuable (40.0% in EAMLs vs. 0.0% in TAMLs, p < 0.001), and TOC ratio was much higher in EAMLs (166.01 ± 64.47%) than that in TAMLs (93.74 ± 46.56%)(p < 0.001), though they did make overlaps with ccRCCs. With either heterogeneous peak enhancement or the presence of pseudocapsule or TOC ratio >97.34% as the criteria to differentiate ccRCCs and EAMLs from TAMLs, the sensitivity and specificity were 80.0% and 87.5%, respectively.
  
  
  CONCLUSIONS
  Qualitative and quantitative CEUS analyses are helpful in the differential diagnosis of ccRCCs, EAMLs, and TAMLs.
authors.affiliation: Department of Ultrasound, Shanghai Institute of Medical Imaging, Zhongshan Hospital, Fudan University, No. 180 Fenglin Road, Shanghai, 200032, China, lu.qing@zs-hospital.sh.cn.
authors.forename: Qing
authors.initials: Q
authors.lastname: Lu
authors.forename: Cui-xian
authors.initials: CX
authors.lastname: Li
authors.forename: Bei-jian
authors.initials: BJ
authors.lastname: Huang
authors.forename: Li-yun
authors.initials: LY
authors.lastname: Xue
authors.forename: Wen-ping
authors.initials: WP
authors.lastname: Wang
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000328:Adult; D000368:Aged; D018207:Angiomyolipoma / Q000000981:diagnostic imaging*; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging*; D003287:Contrast Media; D003937:Diagnosis, Differential; D004848:Epithelium / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010743:Phospholipids; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013459:Sulfur Hexafluoride; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride