title: Angiomyolipoma and renal cell carcinoma: US differentiation.
abstract: OBJECTIVE
  To analyze whether shadowing and other ultrasound (US) features were helpful for distinguishing angiomyolipoma (AML) from renal cell carcinoma (RCC).
  
  
  METHODS
  US images were reviewed of 49 patients with RCC and 35 patients with AML. Each tumor was evaluated for size, location, echogenicity, homogeneity, shadowing, hypoechoic rim, and intratumoral cysts. When available, computed tomographic (CT) scans of AMLs were analyzed for the amount of fat and soft tissue in each lesion.
  
  
  RESULTS
  AMLs tended to be smaller and more frequently echogenic than RCCs, but statistically significant overlap occurred. Shadowing was seen in 12 (33%) AMLs but was not seen in RCCs. Hypoechoic rims and intratumoral cysts were seen only in RCCs (numbers were too small to perform further statistical analysis).
  
  
  CONCLUSIONS
  In hyperechoic renal masses, the presence of shadowing, a hypoechoic rim, and intratumoral cysts are important findings that may help distinguish AML from RCC.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Siegel
authors.forename: W D
authors.initials: WD
authors.lastname: Middleton
authors.forename: S A
authors.initials: SA
authors.lastname: Teefey
authors.forename: B L
authors.initials: BL
authors.lastname: McClennan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018207:Angiomyolipoma / Q000000981:diagnostic imaging*; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography