CSF is made in the choroid plexus of the brain. This area of the brain is vulnerable to a rare type of pediatric cancer called choroid plexus carcinoma. In this disease, CSF accumulates because of a blockage in flow caused by the tumor. This accumulation is called hydrocephalus and is an indicator for other neurological conditions as well.
A lumbar puncture, or spinal tap, is a procedure done to collect cerebrospinal fluid. It can be an important diagnostic tool in some metastatic cancers.
Lumbar punctures can also deliver chemotherapy medications into the CSF, as many chemotherapy drugs do not cross the blood-brain barrier. This method is mostly seen in leukemia cases and is not as common as other means of delivering chemotherapy.