title: Computed tomographic distinction of perirenal liposarcoma from exophytic angiomyolipoma: a feature analysis study.
abstract: OBJECTIVE
  To identify computed tomographic (CT) findings that distinguish perirenal liposarcomas from exophytic angiomyolipomas.
  
  
  METHODS
  We identified CT scans of 20 patients (13 women and 7 men; mean age, 63 years) with either perirenal liposarcoma (n = 11) proven at histopathology or large exophytic angiomyolipomas (n = 9) determined by 2-year stability (n = 6) or histopathology (n = 3). Two independent readers unaware of the final diagnoses recorded the presence of the following CT findings: (1) tumoral vessel extending into the renal cortex, (2) tumoral vessel extending into the renal hilum, (3) renal parenchymal defect at the site of tumor contact, (4) intratumoral hemorrhage, (5) nonfat attenuating intratumoral nodules, and (6) calcification.
  
  
  RESULTS
  A tumoral vessel extending into the renal cortex was seen only in angiomyolipomas (7 and 6 of 9 patients versus 0 and 0 of 11 liposarcomas for readers 1 and 2, respectively; P < 0.005 for both). A parenchymal defect was more commonly seen in angiomyolipomas (7 and 6 of 9 angiomyolipomas versus 1 and 1 of 11 liposarcomas for readers 1 and 2, respectively; P < 0.05 for both). Calcifications were seen by both readers in 6 of 11 liposarcomas but not in any angiomyolipomas (P < 0.05). The other recorded findings were not useful in distinguishing CT features (P > 0.1 for both readers).
  
  
  CONCLUSIONS
  In the evaluation of a fatty perinephric mass at CT, the presence of a tumoral vessel extending into the renal cortex or a renal parenchymal defect at the site of tumor contact strongly favors the diagnosis of exophytic angiomyolipoma, whereas calcifications suggest liposarcoma.
authors.affiliation: Department of Radiology, University of California San Francisco, San Francisco, CA 94143-0628, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Ellingson
authors.forename: Fergus V
authors.initials: FV
authors.lastname: Coakley
authors.forename: Bonnie N
authors.initials: BN
authors.lastname: Joe
authors.forename: Aliya
authors.initials: A
authors.lastname: Qayyum
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Westphalen
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Yeh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018207:Angiomyolipoma / Q000175:diagnosis* / Q000601:surgery; D003287:Contrast Media / Q000008:administration & dosage; D003937:Diagnosis, Differential; D003973:Diatrizoate; D005260:Female; D006801:Humans; D007472:Iohexol; D007668:Kidney / Q000000981:diagnostic imaging / Q000601:surgery; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000601:surgery; D008080:Liposarcoma / Q000175:diagnosis* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D003973:Diatrizoate; D007472:Iohexol