Masked malignant phenotype with a benign appearance: beat-up copy number profile may be the key for hemangioblastoma dissemination.

Dissemination of histologically benign hemangioblastoma is rare; approximately 30 cases have previously been reported, and all cases occurred several months to years after surgical resection. Herein, we report a case of hemangioblastoma in which leptomeningeal dissemination occurred 2 years after hypofractionated radiation therapy (39 Gy/13 fractions). The tumor was treated primarily with radiation without surgical resection. Biopsy of the disseminated lesion confirmed histological diagnosis as histologically benign hemangioblastoma. Ki67 index was not remarkably elevated for hemangioblastomas. In addition, the methylation class determined by the methylation profiling classifier developed by the German Cancer Research Center (DKFZ)/University Hospital Heidelberg/German Consortium for Translational Cancer Research was consistent with that of common hemangioblastomas. However, genetic analyses showed significant gains and losses throughout the whole genome, indicating that highly aberrant copy number profiles may be the key to elucidating this rare but life-threatening clinical entity. Accumulation of more detailed case reports based on the comparison of specimens obtained before and after surgery or radiation is necessary to better understand the pathophysiology of the dissemination phenotype of hemangioblastoma.