Pleomorphic Xanthoastrocytoma (PXA) and Other BRAF-Altered Tumors: Diagnosis and Treatment

MRI of a Pleomorphic Xanthoastrocytoma (PXA) in the brain.

Credit: NCI-CONNECT Staff

Pleomorphic xanthoastrocytoma (PXA) is a very rare type of astrocytoma, a primary central nervous system (CNS) tumor. This means it begins in the brain or spinal cord. PXAs typically have genetic alterations, such as the BRAFV600E mutation, that affect a series of chemical reactions known as the MAPK signaling pathway. These genetic alterations can ultimately help the tumor cells grow and survive. While these genetic changes help form and maintain the tumor, they may also be targeted for treatment.

To get an accurate diagnosis, a piece of tumor tissue will be removed during surgery, if possible. A neuropathologist should then review the tumor tissue.

What are the grades of PXA?

Primary CNS tumors are graded based on the tumor location, tumor type, extent of tumor spread, genetic findings, the patient’s age, and tumor remaining after surgery, if surgery is possible.

These tumors are grouped in two grades (grade 2 or grade 3, also written as grade II or grade III) based on their characteristics.

Grade 2 PXAs are low grade tumors. This means the tumor cells grow slowly.
Grade 3 APXAs are malignant (cancerous). This means they are fast-growing tumors.

What do PXAs look like on an MRI?

PXAs often form fluid-filled cysts in a mural nodule, which means a cyst within solid tissue with a dense appearance on MRI. Grade III PXAs may appear similar to PXAs, but the way they look varies and makes it difficult to tell apart from other primary CNS tumors. The diagnosis of PXA can’t be made by imaging alone because they may look the same as glioblastomas and other high-grade brain cancers.

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What causes PXAs?

Cancer is a genetic disease – that is, cancer is caused by certain changes to genes that control the way our cells function. Genes may be mutated (changed) in many types of cancer, which can increase the growth and spread of cancer cells. The cause of most PXAs is not known. People with gene changes that can be passed down through families such as neurofibromatosis type I and familial melanoma/astrocytoma syndrome, are at increased risk for developing PXAs.

Where do PXAs form?

PXAs usually occur in one of the four lobes of the brain. The temporal lobe is the most common location. Rarely, PXAs can form in the cerebellum, brainstem, and spinal cord. PXAs are usually located close to the surface of the brain tissue. Scientists believe these tumors arise from cells that grow into glial and nerve cells. PXAs can look a variety of ways under the microscope and can be challenging to diagnose, as they share characteristics with other primary brain tumors. Review by an expert neuropathologist is recommended to confirm this diagnosis. Molecular testing will often reveal a BRAF gene change in these tumors.

Do PXAs spread?

Grade II PXAs are slow-growing tumors that usually don’t spread. Grade III PXAs are fast-growing tumors that usually invade brain tissue in the lobe of the brain where they started. It’s rare for PXAs of any grade to spread to other areas of the CNS. There are no reported cases of spread outside of the CNS.

What are symptoms of a PXA?

Symptoms related to PXAs depend on the tumor’s location. Here are some possible symptoms that can occur.

PXA Symptoms

People with Grade II PXAs may have:

Seizures
Epilepsy
Chronic headaches

People with Grade III PXAs may have:

Seizures
Weakness
Numbness
Speech and language changes

Who is diagnosed with PXAs?

PXAs can occur at any age, but tend to happen in young adulthood, and occur slightly more often in males than females. PXAs are more common in people of African descent. An estimated 1,081 people are living with this tumor in the United States.

What is the prognosis of PXAs?

The likely outcome of the disease or chance of recovery is called prognosis.

The relative 5-year survival rate for PXA is 76.2% but know that many factors can affect prognosis. This includes the tumor grade and type, traits of the cancer, the person’s age and health when diagnosed, and how they respond to treatment. If you want to understand your prognosis, talk to your doctor.

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What are treatment options for PXAs?

The first treatment for a PXA is surgery, if possible. The goal of surgery is to obtain tissue to determine the tumor type and to remove as much tumor as possible without causing more symptoms for the person. Grade II PXAs can often be treated by surgery alone.

If they come back after surgery, there is no standard treatment for PXAs. Possible treatments at this time may include radiation, chemotherapy, targeted therapies, or clinical trials. If a BRAF change is present, clinical trials using a drug to target that may also be an option. Treatments are decided by the patient’s healthcare team based on the patient’s age, remaining tumor after surgery, tumor type, and tumor location.

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Referrals

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