Inclusion Criteria:  Participant is 18 years or older. Participant has a Karnofsky Performance Status of >= 60%. Participant has a primary or metastatic brain tumor(s). Participant can have newly diagnosed or recurrent brain tumor(s).  If a participant is requiring more than 3 mg orally every 12 hours (q 12 h) of dexamethasone at the time of signing the consent form, it is anticipated by the neurosurgeon that the participant will be able to taper down their dose of dexamethasone to 3 mg orally q 12 h by 3 days before the surgery.  (Note: If the patient is not able to decrease their dose of dexamethasone to 3 mg orally q 12 h 3 days before surgery, the patient will not be allowed to participate in the study.) Participant must have less than 10 mm of midline shift seen on pre-op brain magnetic resonance imaging (MRI). The neurosurgeon anticipates being able to perform a gross total resection of tumor. Participant is not planning to participate in another clinical trial during the study period. There is no limit to the number of prior therapies for enrollment in this study. All participants must have the ability to understand and the willingness to sign a written informed consent.  Exclusion Criteria:  Participant is unable to undergo a brain MRI. Participant is unable to tolerate dexamethasone. Participant has a chronic or active viral infection of the central nervous system (CNS). Participant has a coagulopathy or bleeding disorder. Participant has an uncontrolled illness including ongoing or active infection. Participant has another active malignancy. A patient has a serious medical or psychiatric illness that could, in the investigator's opinion, potentially interfere with the safety monitoring requirements and completion of treatment according to this protocol.