title: Primary solitary lymphoma of the fourth ventricle.
abstract: BACKGROUND
  Primary central nervous lymphoma(PCNSL) is a rare form of non-Hodgkin lymphoma confined to the central nervous system. Most of the lesions are supratentorial and periventricular, often involving deep structures such as corpus callosum and basal ganglion. Isolated intraventricular lymphoma is rare and only a few case reports. We report, to the best of our knowledge, the seventh case of isolated PCNSL in the fourth ventricle in an immunocompetent patient.
  
  
  METHODS
  A 61-year-old male presenting with 3 months of headache and dizziness followed with unsteady gait for days. The MR imaging of brain revealed a homogeneously enhancing lesion occupying almost the whole 4th ventricle.The tumor was removed subtotally via suboccipital craniotomy. Histopathology revealed the lesion be a diffuse large B-cell lymphoma.
  
  
  CONCLUSIONS
  PCNSL is an important consideration in the differential diagnosis of intracranial mass lesion. The unusual location in surgically accessible fourth ventricle in posterior fossa, the isolation of the tumor may present a compelling indication for surgical resection.
  
  
  CONCLUSIONS
  We suggest that primary lymphoma should be considered with homogenous lesions of the 4th ventricle. Also aggressive surgical resection in this surgically accessible location, instead of biopsy only, is rational.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Kaohsiung Veterans General Hospital, Taiwan, ROC. Electronic address: mccoyhsu@gmail.com.
authors.forename: Huang-I
authors.initials: HI
authors.lastname: Hsu
authors.affiliation: Department of Radiology, Kaohsiung Veterans General Hospital, Taiwan, ROC. Electronic address: phlai@vghks.gov.tw.
authors.forename: Ping-Hong
authors.initials: PH
authors.lastname: Lai
authors.affiliation: Department of Pathology, Kaohsiung Veterans General Hospital, Taiwan, ROC. Electronic address: hhtseng@vghks.gov.tw.
authors.forename: Hui-Hwa
authors.initials: HH
authors.lastname: Tseng
authors.affiliation: Division of Neurosurgery, Department of Surgery, Kaohsiung Veterans General Hospital, Taiwan, ROC; Neurosurgical department, National Defense Medical Center, Taiwan, ROC. Electronic address: sshsu59@yahoo.com.
authors.forename: Shu-Shong
authors.initials: SS
authors.lastname: Hsu
keywords: CNS; Intraventricular tumor; Lymphoma