Diffuse craniospinal seeding from a benign fourth ventricle choroid plexus papilloma. Case report.

Choroid plexus papillomas can metastasize to the subarachnoid space, but extensive metastasis has only been reported when the tumors are malignant. The authors report a case of diffuse, extensive metastasis to the craniospinal leptomeninges from a benign fourth ventricular choroid plexus papilloma in an adult. This 19-year-old woman presented with a 2-year history of headache, blurred vision, diplopia, and ataxia. Magnetic resonance imaging of the brain and spinal cord revealed obstructive hydrocephalus caused by a 4-cm, partially calcified, inhomogeneously enhancing tumor of the fourth ventricle that was displacing the pons, medulla oblongata, and cerebellum. Innumerable cystic lesions of varying size were also seen in the cranial and spinal leptomeninges. Histological examination of the resected fourth ventricular tumor and of a few of the leptomeningeal lesions revealed a benign choroid plexus papilloma and leptomeningeal choroid plexus cysts. This singular case of diffuse and extensive metastasis to the craniospinal leptomeninges from a histologically benign fourth ventricular papilloma adds to the available information about the biological potential of these tumors and expands the differential diagnosis of posterior fossa lesions with subarachnoid metastasis.