title: Extravascular papillary endothelial hyperplasia mimicking neoplasm after radiosurgery:  case report.
abstract: BACKGROUND
  Papillary endothelial hyperplasia (PEH) is a rare form of exuberant reactive endothelial proliferation that can mimic neoplasm. We report the largest series of patients with histologically confirmed intracranial extravascular PEH developing in the field of previous treatment with stereotactic radiosurgery.
  
  
  METHODS
  We collected the clinical, radiological, surgical, and pathological findings from 4 patients in whom intracranial extravascular PEH developed after treatment with stereotactic radiosurgery. In all patients, the development of an enlarging hemorrhagic mass lesion at the site of previous radiotherapy on magnetic resonance imaging was radiographically suspicious for neoplasm and prompted biopsy or resection. All 4 patients elected to undergo biopsy or surgical resection. Histological examination of the biopsy and resection specimens in all patients demonstrated the classic features of PEH.
  
  
  CONCLUSIONS
  The interval to the development of PEH ranged from 5 months to 6 years, 10 months. Clinical follow-up was available for 3 of the 4 patients. None of these 3 patients have demonstrated evidence of recurrence during a mean follow-up period of 22 months (range, 15-30 months). These patients share common radiological features, potentially allowing preoperative diagnosis and improved guidance of clinical management. These cases suggest a link between radiosurgery and the development of PEH. These findings also suggest that PEH should be considered in the differential diagnosis for patients treated with radiosurgery in whom a hemorrhagic mass lesion subsequently develops at or near the site of previous treatment. We think that complete surgical excision is the best treatment for intracranial PEH.
authors.affiliation: Department of Pathology, Stanford University Medical Center, Palo Alto, California, USA. jkaramch@gmail.com
authors.forename: Jason
authors.initials: J
authors.lastname: Karamchandani
authors.forename: Hannes
authors.initials: H
authors.lastname: Vogel
authors.forename: Nancy
authors.initials: N
authors.lastname: Fischbein
authors.forename: Iris
authors.initials: I
authors.lastname: Gibbs
authors.forename: Michael S B
authors.initials: MS
authors.lastname: Edwards
authors.forename: Harsh
authors.initials: H
authors.lastname: Griffith
mesh_terms: D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000473:pathology / Q000601:surgery*; D001932:Brain Neoplasms / Q000601:surgery; D003937:Diagnosis, Differential; D004730:Endothelium, Vascular / Q000473:pathology*; D006801:Humans; D006965:Hyperplasia / Q000209:etiology / Q000473:pathology; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000009:adverse effects*