Inclusion Criteria:

• Age ≥18 years.
• Clinical and radiographic evidence suggesting a diagnosis of a brain tumor.
• Planned neurosurgical procedure resection of suspected or previously diagnosed brain tumor as part of routine clinical care.
• Willing to undergo neurosurgical resection at Mayo Clinic (Rochester, MN).
• Ability to understand and the willingness to sign a written informed consent document.
• Patient is willing to have their Ommaya sampled on at least 2 future occasions.
• Patients is willing to have cerebrospinal fluid (CSF) banked through the neuro-oncology biorepository (requires a separate signature).

 Exclusion Criteria:

• Vulnerable populations: pregnant women, prisoners, or the mentally handicapped.
• Patients who are not appropriate candidates for surgery due to current or past medical history or uncontrolled concurrent illness.
• Prior history of any wound infection.
• Any patient who the surgeon feels is not an optimal candidate for Ommaya reservoir placement. Such reasons may (but need not necessarily) include surgical anatomy clinical evidence of significant immunosuppression, and/or elevated risk of wound infection due to diabetes, smoking history, morbid obesity, or any other concerns.