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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 cells develop very early in an embryo as a baby grows inside the mother. These cells normally travel to the ovaries or testicles and mature to form egg or sperm cells. Sometimes these cells can form tumors. Gonadal germ cell tumors form in the ovaries and testicles. When germ cells travel to places other than the sex organs, the cells can form extragonadal germ cell tumors. These tumors can occur in the brain (intracranial) and other parts of the body such as the chest or abdomen (extracranial germ cell 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:
Germinomas are the most common type of germ cell tumor. Children with germinoma have a 90% chance of cure.
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 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.
Doctors test for germ cell tumors of the central nervous system in several ways.
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).
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:
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:
|Intermediate||Germinoma with syncytiotrphoblastic giant cells
Mixed tumors (germinoma or teratoma)
Teratoma with malignant transformation
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.
Chemotherapy is usually used in combination with radiation therapy to treat germ cell tumors. Germinomas respond well to chemotherapy, which may allow a lower dose of radiation to be used. High-dose chemotherapy with stem cell rescue may be tried as a treatment for recurrent disease.
Radiation therapy is used as a main therapy for germ cell tumors. The method and dose of radiation therapy depends on the type of germ cell tumor, its location, and whether it has spread. The child’s age is an important consideration in the use of radiation to treat childhood brain cancers to reduce the risk of late effects of therapy.
Because of the location of the tumor and the tendency of the tumor to respond to other treatments, surgery is not usually used to treat germinoma. However, because non-germinomas are more difficult to treat, surgery may be used to remove as much of the tumor as possible in addition to chemotherapy and radiation therapy.
In some cases, a patient with a germ cell tumor will have surgery to place a shunt in the brain to keep fluid from building up (hydrocephalus). A shunt is a small tube that drains cerebrospinal fluid (CSF) so that the fluid can be removed from the brain. Excess fluid causes increased intracranial pressure and can cause many of the symptoms associated with brain tumors. The shunt may be temporary or permanent.
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.
The pituitary gland is called the “master gland” because it is responsible for many hormones and control of other glands. Low pituitary function can lead to a number of problems. These problems may include delayed growth and/or puberty, fatigue, decreased thyroid function, and fertility problems.
Reviewed: June 2018