Diagnosis of Medulloblastoma
Medulloblastoma is the most common malignant brain tumor in children, with about 400-500 new diagnoses per year in the United States.
The signs and symptoms of medulloblastoma prompt an evaluation that includes a neurological exam by a doctor, as well as magnetic resonance imaging (MRI). Sometimes a computed tomography (CT) scan is also ordered.
Most often a lumbar puncture (spinal tap) will also be done. This involves collecting cerebrospinal fluid for testing to see if medulloblastoma cells are floating in the spinal fluid.
Hydrocephalus with Medulloblastoma
Often with medulloblastoma there is pressure in the brain being caused by too much cerebrospinal fluid. This is a condition called hydrocephalus. If this is the case, a shunt may be placed to relieve that pressure before surgery to remove the tumor.
Surgery for Medulloblastoma
Surgery is required to diagnose medulloblastoma, and is also the first treatment. The goal is to remove as much of the tumor as possible. This is often referred to as tumor resection.
After the tumor has been removed, a portion of it will be sent to a lab for testing.
Your care team will then take all of the information they’ve gathered — the MRI of the brain, the MRI of the spine, the lumbar puncture results, and the results of the tumor pathology (analysis) at the lab — and use it to help determine the direction for next steps in treatment.
Medulloblastoma Tumor Staging
Cancer staging refers to how large a tumor is and if it has spread. Stages are given a number from 0-4. The higher the number, the more advanced the cancer is.
In medulloblastoma, these are labeled as M0-M4 and are classified as follows:
- M0 – The tumor is in one place. There are no signs that it has spread to other parts of the body.
- M1 – Tumor cells were found in the cerebrospinal fluid.
- M2 – The tumor has spread to the brain.
- M3 – The tumor has spread to the spine.
- M4 – The tumor has spread outside the central nervous system
Grading a Medulloblastoma Tumor
A pathologist looks at body tissues and performs lab tests to help your doctor reach a diagnosis. Pathologists grade brain tumors on a 1 to 4 scale. These numbers indicate how aggressive they are. Lower numbers indicate less-aggressive tumors.
All medulloblastomas are grade 4 tumors, because they are malignant (cancerous), aggressive tumors. You may also see this written as grade IV.
A pathologist also examines the tumor to determine its subtype. Knowing the medulloblastoma subtype provides further details on prognosis and treatment of the cancer.
Identifying the Medulloblastoma Subtype in Children
Medulloblastomas are divided into one of four subtypes based on their genetic features:
WNT-activated
About 10% of patients have this subtype of medulloblastoma, making it the least common subtype. It has the best prognosis of the four groups. People with Turcot syndrome have an increased risk of developing WNT-activated medulloblastoma. It is most often diagnosed in older kids and teens, rarely in infants, and tends not to spread (metastasize).
SHH-activated
The SHH group of medulloblastomas make up about 30% of diagnoses. This group is named after the Sonic hedgehog (SHH) signaling pathway (which is named after the video game character). That pathway is thought to drive tumor initiation in many, if not all, such cases. People with Gorlin syndrome have an increased risk of developing SHH-activated medulloblastoma. This subtype is most often found in infants and adults, and tends not to spread (metastasize).
Group 3 (non-WNT/non-SHH)
Group 3 tumors account for about 25% of all cases of medulloblastoma. Chance of spreading (metastasis) is high. Group 3 tumors occur more commonly in males than females, and are found in infants and children. They are rarely found in teens, and never in adults.
Group 4 (non-WNT/non-SHH)
Group 4 medulloblastoma is diagnosed most often, making up about 35% of all cases. They are found in people of all ages, but rarely in infants. Group 4 tumors are found in more males than females. Metastasis occurs often.
Recently Diagnosed With Medulloblastoma?
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