Spontaneous seeding of medulloblastoma: results of cerebrospinal fluid cytology and arachnoid biopsy from the cisterna magna.

Five children with cerebellar medulloblastoma underwent cytological study for neoplastic cells in the cerebrospinal fluid (CSF) from the lateral ventricle and cisterna magna and biopsy of the arachnoid of the cisterna magna before the manipulation of a medulloblastoma. In all cases, seeding of neoplastic cells was present in the CSF or arachnoid of the cisterna magna, whereas the ventricular fluid was negative for neoplastic cells. This study suggests that medulloblastoma seeds spontaneously into the subarachnoid space, thus supporting the need for postoperative whole neuraxis radiation.