Often, the appearance on the MRI scan is highly suggestive of whether or not a tumor is benign or malignant, but in some cases, it is necessary to obtain a biopsy to be sure.
For some tumors, the appropriate next step is surgery to biopsy and remove it. For other cases, it may be appropriate to biopsy only. For other patients, radiosurgery (a form of radiation therapy) may be appropriate without surgery. Finally, in some patients, doctors recommend no treatment, but merely follow up scans from time to time.
All these decisions depend on details of what was found on the MRI scan and what the other medical issues are with the patient.