title: Pilocytic Astrocytoma of Fornix Mimicking a Colloid Cyst: Report of 2 Cases and Review of the Literature.
abstract: BACKGROUND
  Colloid cyst is a gelatin-containing cyst in the brain almost always found in the third ventricle. The specific shape and location of these cysts, a round well-delineated mass in the rostral part of the third ventricle adjacent to the foramen of Monro, on imaging are the main findings for diagnosis. Several masses of the third ventricle masquerading colloid cysts on images have been reported. Based on different surgical approaches, preoperative misdiagnosis of colloid cyst may have great impact on prognosis.
  
  
  METHODS
  We report 2 cases that presented with severe headache and hydrocephalus, and their preoperative images were highly indicative of colloid cyst.
  
  
  RESULTS
  Histopathologic investigations after tumor resection showed pilocytic astrocytoma of fornix in both cases.
  
  
  CONCLUSIONS
  Fifteen cases of colloid cyst misdiagnosis with other masses have been reported thus far; among them, 2 cases were pilocytic astrocytoma. In this study we report 2 other cases. Furthermore, we discuss additional clues helping to differentiate pilocytic astrocytoma from colloid cyst on images.
authors.affiliation: Department of Neurosurgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Guive
authors.initials: G
authors.lastname: Sharifi
authors.affiliation: Neuroscience Division, Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Rahmanzadeh
authors.affiliation: Department of Neurosurgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Lotfinia
authors.affiliation: Department of Neurosurgery, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Electronic address: raminrahmanzade@sbmu.ac.ir.
authors.forename: Ramin
authors.initials: R
authors.lastname: Rahmanzade
mesh_terms: D001254:Astrocytoma / Q000150:complications / Q000000981:diagnostic imaging*; D001932:Brain Neoplasms / Q000150:complications / Q000000981:diagnostic imaging*; D002648:Child; D056364:Colloid Cysts / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D020712:Fornix, Brain / Q000000981:diagnostic imaging*; D006261:Headache / Q000209:etiology; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology; D008279:Magnetic Resonance Imaging; D008297:Male; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Colloid cyst; Fornix; Misdiagnosis; Pilocytic astrocytoma