BACKGROUND AND IMPORTANCE:: 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 prior treatment with stereotactic radiosurgery. CLINICAL PRESENTATION:: We collected the clinical, radiological, surgical, and pathologic findings in four cases of patients who developed intracranial extravascular PEH following treatment with stereotactic radiosurgery. In all cases the development of an enlarging hemorrhagic mass lesion in the site of prior radiotherapy on MRI was radiographically suspicious for neoplasm and prompted biopsy or resection. In all four cases the patients elected to undergo biopsy or surgical resection. Histologic examination of the biopsy and resection specimens in all cases demonstrated the classic features of PEH. CONCLUSION:: The interval to the development of PEH ranged from five months to six years and ten months. Clinical follow up was available for three of the four patients. None of these three patients has demonstrated evidence of recurrence during a mean follow-up period of 22 months (15-30 months). These cases share common radiological features, potentially allowing for pre-operative 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 who subsequently develop a hemorrhagic mass lesion at or near the site of prior treatment. We think that complete surgical excision is the best treatment for intracranial PEH.
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