A Patient-Friendly Guide To Brain Biopsy
- When an MRI or CT scan shows a suspicious mass in the brain, your medical team may recommend a brain biopsy. A biopsy is a procedure where a small piece of tissue is removed so a pathologist can look at it under a microscope.
- Stereotactic needle biopsy is the most common type of biopsy used. It is minimally invasive and imaging (MRI or CT) helps the surgeon map the safest path to the tumor. A tiny incision is made, and a narrow needle is guided precisely to the mass. Small samples of tissue are removed — and then the incision is closed with a stitch or staple.
- An open biopsy may be used when the tumor is close to the surface or when the surgeon believes a larger sample is needed.
- After biopsy, most patients go home the same day or the next morning.
“When a patient with a brain tumor is initially diagnosed, they usually present after acute symptoms, most commonly a seizure, and the patient will come into the emergency room, be evaluated [and] as part of that evaluation, brain imaging is obtained and that’s often with an MRI of the brain,” Dr. Nicolas Gonzalez Castro, a neuro-oncologist from Dana Farber Cancer Institute, tells SurvivorNet.
Read MoreHow Is A Brain Biopsy Performed?
A brain biopsy is usually done by a neurosurgeon using one of two main methods.- Stereotactic Needle Biopsy (most common): This is a minimally invasive procedure. The entire process is planned with millimeter-level accuracy to avoid injury to healthy brain tissue. You are placed in a special head frame or a non-invasive guidance system is used. Imaging (MRI or CT) helps the surgeon map the safest path to the tumor. A tiny incision is made, and a narrow needle is guided precisely to the mass. Small samples of tissue are removed. And finally, the incision is closed with a stitch or staple.
- Open Biopsy (less common): This is used when the tumor is close to the surface or when the surgeon believes a larger sample is needed. A small opening in the skull (a craniotomy) is made. The surgeon then takes a piece of tissue directly. You may stay in the hospital a bit longer than with a needle biopsy.
After biopsy, most patients go home the same day or the next morning. Headache, fatigue, or mild soreness at the incision site are common. Your doctors will review the pathology results with you in several days.
Possible Biopsy Complications
Brain biopsies are generally safe, but — as with any procedure — risks exist. Your neurosurgeon will discuss these with you.
Possible complications include:
- Bleeding or hemorrhage in the brain (small risk)
- Infection
- Swelling around the biopsy site
- Seizures
- Transient neurological symptoms, such as weakness or changes in speech
The overall chance of a serious complication is low, usually less than a few percent, especially when done at experienced centers.
How Is A Glioma Diagnosis Made?
Once the tissue is removed, a specialized doctor called a neuropathologist studies it under the microscope.
They determine:
- Whether the tumor is a glioma
- What type of glioma (such as astrocytoma or oligodendroglioma)
- The tumor’s grade (how aggressive it appears)
- Whether there are features like necrosis (cell death) or rapid cell division
However, today’s diagnosis goes far beyond what the cells look like. Modern glioma classification depends heavily on molecular markers — special genetic changes inside the tumor cells.
Glioma Molecular Markers
Molecular markers help doctors predict how the tumor behaves and what treatments may work best.
The most commonly assessed markers include:
- IDH Mutation (IDH1 or IDH2): This mutation divides gliomas into IDH-mutant and IDH-wild-type. IDH-mutant tumors generally have a better prognosis.
- 1p/19q Codeletion: This is seen almost exclusively in oligodendrogliomas. Patients with this marker often respond well to radiation and chemotherapy
- MGMT Promoter Methylation: This helps predict how well the tumor may respond to temozolomide (a common chemotherapy drug)
- TERT Promoter Mutation, ATRX Loss, EGFR Amplification, and others: These additional markers fine-tune the diagnosis and help guide care in more complex cases.
Your pathology report will combine the tissue appearance and molecular findings to determine the exact WHO tumor type, which guides treatment planning.
Why Is IDH Important?
IDH is one of the most important biomarkers in glioma care.
“Gliomas that have IDH mutations tend to grow more slowly than tumors that do not have them … specifically, glioblastoma, which is the most common and aggressive of the gliomas, a tumor that usually develops in older patients in their seventh or eighth decade of life,” Dr. Castro explains.
“Those tumors do not have IDH mutations and grow at a much faster rate than tumors that have IDH mutations,” he adds.
IDH-mutant tumors grow more slowly and behave differently than IDH-wild-type tumors. Patients with IDH-mutant gliomas typically live longer and respond better to treatment.
New therapies targeting IDH are being studied and may be very beneficial for certain patients. Under modern WHO guidelines, IDH status helps determine whether the tumor is classified as: IDH-mutant astrocytoma, oligodendroglioma (IDH-mutant with 1p/19q codeletion), glioblastoma, or IDH-wild-type.
This single marker has a profound impact on both diagnosis and treatment planning.
Questions To Ask Your Doctor
- What can I do to prepare for a biopsy?
- What possible side effects and complications should I be aware of?
- When can I expect results?
- What are the next steps in treatment planning after the biopsy?
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