title: Renal Cell Carcinomas: Sonographic Appearance Depending on Size and Histologic Type.
abstract: OBJECTIVE
  Prior studies have demonstrated that approximately 10% of malignant renal cell carcinomas are as echogenic as angiomyolipomas on sonography. However, a recent presentation suggested that small (<1-cm) echogenic renal masses are always angiomyolipomas or other benign entities. We therefore examined our own cases of renal cell carcinoma, with corresponding sonography, to confirm that some renal cell carcinomas may also be detected as hyperechoic masses on sonography.
  
  
  METHODS
  Institutional Review Board approval and Health Insurance Portability and Accountability Act compliance were maintained for this retrospective review of 91 pathologically proven cases of renal cell carcinoma, with corresponding sonography. Tumors were first differentiated by histologic cell type (clear cell, papillary, and chromophobe). Tumors were then stratified according to 2 size group parameters, falling into those that were 3 cm or larger and those that were smaller than 3 cm in diameter, with the less than 3-cm group further subdivided into 2 cm or smaller and greater than 2 cm. Tumor echogenicity was graded on a 5-point scale with respect to the renal parenchyma.
  
  
  RESULTS
  Forty-six tumors (51%) were 3 cm in diameter or smaller, and most were found to be either isoechoic (35%) or mildly hyperechoic (26%) to the surrounding renal parenchyma. Of tumors smaller than 2 cm, most were either mildly hyperechoic (29%) or as hyperechoic as renal sinus fat (very hyperechoic; 29%). Tumors larger than 3 cm were found most often to be either isoechoic (49%) or mildly hyperechoic (33%), with only 4% found to be very hyperechoic.
  
  
  CONCLUSIONS
  The sonographic appearances of renal cell carcinomas include a small population that are very hyperechoic on sonography and thus could potentially be misdiagnosed as angiomyolipomas.
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA.
authors.forename: Kunal
authors.initials: K
authors.lastname: Sidhar
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA. jpmcgahan@ucdavis.edu.
authors.forename: John P
authors.initials: JP
authors.lastname: McGahan
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Early
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Corwin
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA.
authors.forename: Ghaneh
authors.initials: G
authors.lastname: Fananapazir
authors.affiliation: Department of Radiology, University of California, Davis Health System, Sacramento, California USA.
authors.forename: Eugenio O
authors.initials: EO
authors.lastname: Gerscovich
mesh_terms: D000368:Aged; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
keywords: angiomyolipoma; echogenicity; kidney neoplasm; renal cell carcinoma; renal mass; sonography