title: Angiomyolipoma with minimal fat: differentiation from papillary renal cell carcinoma by helical CT.
abstract: OBJECTIVE
  To evaluate whether helical computed tomography (CT) images can be used to differentiate angiomyolipomas (AMLs) with minimal fat from papillary renal cell carcinomas (PRCCs) based on their morphological characteristics and enhancement features.
  
  
  METHODS
  This retrospective study was approved by the institutional review board. Informed consent was waived. Forty-four patients (21 with AMLs with minimal fat and 23 with PRCCs) who underwent enhanced helical CT before total or partial nephrectomy were included. Two radiologists, who were blinded to the histopathology results, read the CT images and recorded the attenuation value, morphological characteristics, and enhancement features of the tumours, which were subsequently evaluated. An independent samples t-test, χ(2) test, and rank sum test were performed between the tumours. The predictive value of a CT finding was determined by multivariate logistic regression analysis.
  
  
  RESULTS
  AML with minimal fat had an apparent female prevalence (p < 0.01). Intra-tumoural vessels were noted in 11 cases of AML with minimal fat and three PRCC cases (p < 0.01). The unenhanced attenuation characteristic was significantly different between the two diseases (p < 0.001). The absolute attenuation values (AAVs) and the corrected attenuation values (CAVs) of the AML with minimal fat group of unenhanced and two phases of enhanced images were greater compared with that of the PRCC group (p < 0.05). After contrast medium injection, the tumour enhancement value (TEV) of the AML with minimal fat group in the corticomedullary phase was greater than that of the PRCC group (p < 0.01). Most cases of both tumour types demonstrated early enhancement characteristics; the enhancement value of the AML with minimal fat group was greater compared with that of the PRCC group (p < 0.01). The unenhanced attenuation characteristic, intra-tumoural vessels, and CAVs of unenhanced and early excretory phase scans were valuable parameters to differentiate between AML with minimal fat and PRCC tumours by multivariate logistic regression analysis (p < 0.05 for all).
  
  
  CONCLUSIONS
  The unenhanced attenuation characteristic, intra-tumoural vessels, and the attenuation values of unenhanced and early excretory phase scans are valuable parameters in differentiating AML with minimal fat from PRCC at CT.
authors: Department of Radiology, First Affiliated Hospital of China Medical University, Shenyang, China.
authors: Y-Y
authors: YY
authors: Zhang
authors: S
authors: S
authors: Luo
authors: Y
authors: Y
authors: Liu
authors: R-T
authors: RT
authors: Xu
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D018207:Angiomyolipoma / Q000000981:diagnostic imaging* / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000601:surgery; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000379:methods*; D055815:Young Adult