Germ Cell Tumors of the Brain

During normal development of an embryo and fetus, germ cells usually become eggs (in the female) or sperm (in the male). However, if germ cells travel to the brain by mistake, they can become tumors. Germ cell tumors can be benign or malignant. They’re rare, accounting for approximately 4 percent of pediatric brain tumors.

Types & Stages

There are three main types: 

• Germinomas. A type of tumor that begins in germ cells (cells that form sperm or eggs). Germinomas can occur in the ovaries or testicles or other parts of the body, but they occur most often in the central nervous system (brain and spinal cord). This happens when a germ cell travels to the brain during fetal development and later becomes a germ cell tumor. Some germinomas make a hormone called beta-human chorionic gonadotropin (beta-HCG). Germinomas are usually malignant (cancer) but tend to grow and spread slowly and can usually be cured. They respond well to treatment.
   
• Non-germinomatous tumors. These tumors secrete chemicals into the spinal fluid and bloodstream. They require more intensive treatment than germinomas. There are sub-types of non-germinomatous germ cell tumors, including:
   
  • Teratomas. Tumors made up of tissues, such as hair, muscle and bone.
     
  • Choriocarcinoma. A rare, aggressive type of cancer that develops from the placental tissue after pregnancy.
     
  • Endodermal sinus tumors. Also called yolk sac tumors, they occur most often in the ovary or testicle, but they may also occur in other areas of the body, such as the chest, abdomen or brain. They tend to grow quickly and spread to other parts of the body if not treated. Endodermal sinus tumors are the most common malignant germ cell tumor in children.
     
  • Embryonal carcinoma. A rare form of testicular cancer.
     
• Mixed germ cell tumors. These include aspects of both germinomas and non-germinomatous tumors. 

Signs & Symptoms

Symptoms of germ cell tumors typically depend on where they have developed in the brain. For tumors in the pineal gland region, children can have the following symptoms:

• hydrocephalus (swelling of the brain)
• headache
• vomiting
• fatigue
• behavioral or cognitive changes
• uncoordinated body movement (ataxia)
• vision changes, including double vision and difficulty looking up

For tumors in the suprasellar or pituitary gland region, common symptoms include:

• diabetes insipidus (an uncommon disorder characterized by intense thirst and the passing of large amounts of urine)
• delayed puberty
• early (precocious) puberty
• stunted growth
• vision changes, including loss of peripheral vision or decrease in vision

Diagnosis

Your child’s doctor may order a number of different tests including:

• Magnetic Resonance Imaging (MRI). An MRI is the primary imaging test to detect and diagnose germ cell tumors. 
   
• Computed Tomography (CT). Although an MRI is often the first choice in neuroimaging, a CT scan relies on X-rays to create detailed cross-sectional brain images to help evaluate a tumor’s size and location. CT scans are also helpful in identifying hydrocephalus.
   
• Lumbar puncture. Also known as a spinal tap, a lumbar puncture involves a needle inserted into the lower back to collect cerebrospinal fluid (CSF) to test for the presence of cancerous cells. This test can detect whether your child’s tumor has spread within the central nervous system (CNS).
   
• Blood tests. Germ cell tumors release high markers of Alpha-fetoprotein (AFP) or Beta-human chorionic gonadotropin (hCG) in the blood or CSF that help diagnose certain them.

Treatment    

Treatments for germ cell brain tumors include:

• Surgery. Your child’s doctor might initially use surgery to biopsy the tumor and form a complete diagnosis. Depending on the germ cell tumor type, they may recommend further surgery to remove as much of the tumor as possible. They may also relieve pressure from hydrocephalus with:
   
  • Endoscopic third ventriculostomy (ETV). Surgeons create a small hole that allows fluid to flow around the blockage.
     
  • Ventriculo-peritoneal shunt (VP shunt). In some cases, children may have an alternative procedure in which a tube is placed in the ventricles to the abdomen to drain excess fluid into the stomach.
     
• Chemotherapy. Chemotherapy treatment involves medications that interfere with a cancer cell’s ability to grow or reproduce. Doctors use it to shrink tumors and eliminate remaining cancer cells. Different groups of chemotherapy drugs work in different ways. They’re generally systemic treatments. Your child may receive chemotherapy in the following ways:
  • orally, as a pill to swallow
  • intramuscularly, as an injection into the muscle or under the skin
  • intravenously (IV), as a direct injection into the bloodstream
  • intrathecally, as a direct injection into the spinal fluid
     
• Radiation therapy. Doctors may use radiation therapy, which involves using high-energy waves to shrink tumors or damage and destroy cancer cells.

Causes & Risk Factors

The cause of germ cell brain tumors is not well known. Risks include:

• Gender. They’re often diagnosed during puberty and tend to affect boys more than girls.
• Age. Around half occur in children between the ages of 10 and 15.

Screening

There is no screening plan for germ cell tumors, so it’s usually only done when a child develops related symptoms.