title: Horseshoe kidney presenting as a retroperitoneal mass. Report of a case diagnosed by fine needle aspiration cytology.
abstract: BACKGROUND
  Horseshoe kidney is a renal congenital anomaly. It is the result of the fusion of either upper or lower poles of both kidneys, appearing as a horseshoe-shaped structure. This anomaly is very frequent: it can be found in about 1 of every 50-1,000 autopsies).
  
  
  METHODS
  Computed tomography performed routinely after pancreatitis in a 37-year-old female showed a retroperitoneal mass of uncertain origin. Fine needle aspiration cytology (FNAC) smears evidenced normal renal tissue. Urography confirmed the diagnosis of horseshoe kidney.
  
  
  CONCLUSIONS
  This is the first reported case of horseshoe kidney diagnosed by FNAC. It demonstrates the utility of FNAC for diagnosis of retroperitoneal masses, especially if they are asymptomatic.
authors.affiliation: Department of Pathology, University Hospital 12 de Octubre, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Benito
authors.forename: J
authors.initials: J
authors.lastname: Vargas
authors.forename: P
authors.initials: P
authors.lastname: de Agustín
mesh_terms: D000328:Adult; D001707:Biopsy, Needle / Q000379:methods; D000013:Congenital Abnormalities / Q000453:epidemiology / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D015994:Incidence; D007668:Kidney / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology*; D010195:Pancreatitis / Q000000981:diagnostic imaging; D012186:Retroperitoneal Neoplasms / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D014567:Urography