Germ Cell Tumors (Brain)

What are intracranial germ cell tumors?

Intracranial germ cell tumors (GCT) are rare tumors that develop in the brain. They are most often diagnosed in children and young adults. These tumors account for about 3-5% of childhood brain tumors.

Germ cell tumors most often develop in one of two brain regions: pineal or suprasellar. The pineal region of the brain contains the pineal gland. The suprasellar region is located near the pituitary gland. Because of its location, suprasellar germ cell tumors usually affect hormone function. If the tumor is close to the optic nerve, vision may also be affected. Intracranial germ cell tumors do not usually spread outside the central nervous system (CNS).

Intracranial germ cell tumors of the CNS are often classified as germinoma or nongerminomatous germ cell tumor (NGGCT). Types of CNS germ cell tumors include: 

• Germinoma
• Non-germinoma
  • Embryonal carcinoma
  • Yolk sac tumor / endodermal sinus tumor
  • Choriocarcinoma
  • Teratoma (immature and mature)
  • Mixed germ cell tumors

Germinomas are the most common type of germ cell tumor. Children with germinoma have a 90% chance of cure.

Germ cell tumors are usually treated with combination of chemotherapy and radiation therapy. The location of the tumor usually makes it difficult to treat with surgery.

Risk factors and causes of intracranial germ cell tumor

Most (90%) of germ cell tumors occur in patients younger than 20 years of age, and most occur in early adolescence. Germ cell tumors are 2-3 times more common in boys than in girls. Germ cell tumors located in the pineal region occur mostly in boys and are usually germinomas. NGGCTs and germinomas arise with equal frequency in the suprasellar region. Boys and girls are equally affected by tumors in the suprasellar region.

Signs and symptoms of intracranial germ cell tumor

Signs and symptoms of a germ cell brain tumor depend on the tumor size and location. The tumor may cause fluid to build up (hydrocephalus), causing increased pressure in the brain. Tumors near the pituitary gland may affect hormone production. If the tumor is close to the optic nerve, vision can be affected.

As the tumor grows, it may block the normal flow of cerebrospinal fluid. This causes a build up of fluid within the brain known as hyrodcephalus. The fluid causes the ventricles to widen and increases pressure on the brain (intracranial pressure). Many of the symptoms of germ cell tumors in the pineal region are due to the increased pressure against brain tissue.

Diagnosis of intracranial germ cell tumor

Doctors test for germ cell tumors of the central nervous system in several ways.  

• A health history and physical exam helps doctors learn about symptoms, general health, past illness, and risk factors.
• Blood chemistry and hormone studies are used to look at substances in the blood and urine. Doctors will check levels of glucose in the blood and electrolytes such as potassium and sodium. An endocrine panel will test for abnormal levels of pituitary hormones.
• A neurological exam examines the function of the brain, spinal cord, and nerves. These tests measure different aspects of functioning including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
• Imaging tests such as magnetic resonance imaging (MRI) and computerized tomography (CT) are used to help identify the tumor and look for changes in the brain. MRI of the brain and spinal cord is the main imaging technique usually used to diagnose intracranial germ cell tumor and determine if there is spread of the tumor within the CNS. 
• A lumbar puncture is performed to look for cancer cells in the cerebrospinal fluid.
• The blood and cerebrospinal fluid are tested to look for substances released by certain tumors, called tumor markers. Tumor markers that can be helpful in diagnosing some types of germ cell tumor include alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (β-hCG). 
• A biopsy is usually performed to diagnose germ cell tumor. In a biopsy, a small sample of the tumor is removed during surgery. A pathologist looks at the tissue sample under a microscope to identify the specific type of germ cell tumor.

Staging of intracranial germ cell tumor

There is no standard staging for germ cell tumor in the brain or spinal cord. The tumor is described as newly diagnosed or recurrent. A germ cell tumor of the brain can spread to other parts of the central nervous system including brain, spine, and cerebrospinal fluid. It does not usually spread outside the central nervous system (CNS).

Prognosis for intracranial germ cell tumor

Germinomas in children usually respond well to treatment, and the survival rate is about 90%.

Factors that influence prognosis for intracranial germ cell tumors include:

• Age of the child
• Type of germ cell tumor
• The type and level of tumor markers
• Location of the tumor
• Whether the tumor has spread within the brain and spinal cord or to other parts of the body
• Whether the tumor has recurred

Prognosis by tumor type

Certain types of germ cell tumors are associated with a better outcome than other types. However, other factors also affect treatment and prognosis. Here is a general guide based on type:

Treatment of intracranial germ cell tumor

Treatment for germ cell tumor depends on several factors including the size and location of the tumor, the child’s age, and the type of tumor. The main treatments for germ cell tumors are chemotherapy and radiation therapy.

Life after intracranial germ cell tumor

Periodic imaging is used to monitor patients long-term with the schedule based on type of tumor and response to treatment. Follow-up care should include appropriate rehabilitation and neurological consultation.

Patients with germ cell tumors of the brain are at risk for long-term problems in endocrine function including diabetes insipidus and disturbances in pituitary gland function (hypopituitarism). Ongoing monitoring of hormone levels is important, and patients may need medicines including hormone replacement.

More: Life After Brain Tumors