title: [A case of orbital granular cell tumor originating from the inferior oblique muscle].
abstract: OBJECTIVE
  We treated a case of orbital granular cell tumor originating from the inferior oblique muscle.
  
  
  METHODS
  A 55-year-old woman complained of diplopia and induration of the left lower eyelid. Downward rotation of the left eye was restricted. Imaging study results including MRI were compatible with orbital tumor. The tumor was removed by an anterior approach under local anesthesia. Because the tumor was continuous with the inferior oblique muscle, the inferior oblique muscle was unavoidably resected. A histopathological examination showed acidophilic granulation in the cytoplasm of the tumor cells. Striae of the muscle were present at the part of the tumor connecting with the inferior oblique muscle. The S-100 protein test was positive for tumor cells in immunochemical staining. According to these histopathological findings, a diagnosis of orbital granular cell tumor originating from the inferior oblique muscle was made. There has been no local recurrence after a follow-up of 2 years.
  
  
  CONCLUSIONS
  Orbital granular cell tumor is known to arise from extraocular muscles, and to progress in an invasive manner. When the orbital granular cell tumor is removed, pain control, vagovagal reflexes such as bradycardia, and the possibility of resection of extraocular muscles should be considered.
authors.affiliation: Department of Ophthalmology, Tokyo Medical University, Japan. kasa-ken@tokyo-med.ac.jp
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Kasai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Goto
authors.forename: Takuya
authors.initials: T
authors.lastname: Osanai