Pineoblastoma is a very rare brain tumor that develops in the pineal gland. The pineal gland is a tiny structure found deep within the brain. The main pineal gland function is to release melatonin, a hormone that controls sleep.
The pineal gland is part of the endocrine system. It is located near the center of the brain. It is a tiny gland, about the size of a grain of rice. The main job of the pineal gland is to produce the hormone melatonin. The pineal gland receives nerve signals based on light perceived by the eye. Darkness causes the release of melatonin. Melatonin helps to regulate the body’s sleep/wake cycles. Melatonin also helps to control the release of certain reproductive hormones from the pituitary gland such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are important for fertility and reproductive health.
Pineoblastoma is most common in children and young adults. However, it is a rare tumor. Pineoblastomas account for less than 1% of childhood brain tumors. About half of tumors that occur in the pineal gland are pineoblastomas. Other tumors that can occur in the pineal gland include germ cell tumors, gliomas, and benign pineal parenchymal tumors.
Pineoblastomas are usually treated with surgery, radiation therapy, and chemotherapy. Because of the location of the tumor, pineoblastoma can be hard to treat. The 5-year survival rate for childhood pineoblastoma is about 60-65%.
Symptoms of pineoblastoma
Signs and symptoms of pineoblastoma depend on the tumor size and spread to other parts of the brain. Often, the tumor causes cerebrospinal fluid to build up (hydrocephalus) and puts pressure on the brain.
Pineoblastoma symptoms may include:
Nausea and vomiting
Changes in energy level, fatigue
Problems with coordination, balance, or movement
Change in eye movements, especially an inability to look upwards
The brain has a connected set of fluid-filled openings, called ventricles. As a pineal gland tumor grows, it can press on one of these chambers and block the normal flow of cerebrospinal fluid. This causes a buildup of fluid within the brain known as hydrocephalus. The fluid increases pressure on the brain (intracranial pressure). Many of the symptoms of pineal tumors are due to the increased pressure against brain tissue.
Diagnosis of pineoblastoma
Doctors test for pineoblastoma in several ways.
A physical exam and medical history help doctors learn about symptoms, general health, past illness, and risk factors.
Risk Factors: Pineoblastomas are most common in children ages 10 and younger. In most cases, the cause of pineoblastoma is unknown. Rarely, pineoblastoma can occur in children with bilateral retinoblastoma, a cancer associated with a change in the gene RB1. DICER1 syndrome may also increase risk for pineoblastoma. Families may be referred to a genetic counselor if needed.
A neurological exam measures different aspects of brain function including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
Imaging tests such as magnetic resonance imaging (MRI) are used to help identify the tumor. The images give information about the size and location of the tumor and help doctors better understand what areas of the brain might be affected.
A lumbar puncture is used to look for cancer cells in the cerebrospinal fluid.
The blood and cerebrospinal fluid may be tested to look for substances released by certain tumors, called tumor markers. Tumor markers such as alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (β-hCG) may indicate germ cell tumor which can also occur in the pineal region.
A biopsy is usually performed to diagnose pineoblastoma. 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 pineal gland tumor.
Grading and staging of pineoblastoma
There is no standard staging for pineoblastoma. However, doctors may classify the tumor by spread of disease. Pineoblastoma may spread through the cerebrospinal fluid in 10-20% of cases. It rarely spreads to other parts of the body outside the central nervous system.
Pineal gland tumors are classified by how they look under the microscope. The more abnormal tumor cells look, the higher the grade. Pineoblastomas are high-grade (grade IV) tumors.
Successful removal of the tumor and treatment with radiation therapy are associated with better outcomes for children with pineoblastoma.
Factors that affect chance of cure include:
Age at diagnosis. Older children (over 3 years of age) may have better outcomes compared to younger children.
Whether the cancer has spread. Cancer that has metastasized or spread to other parts of the brain or spinal cord is harder to treat.
If surgery can completely remove the tumor. Children who have gross total resection with no visible tumor after surgery have the best chance of cure.
If the cancer is new or if it has come back. Recurrent disease is hard to treat. If relapse occurs, the disease is often widespread and progresses quickly.
Survival rates for newly diagnosed pineoblastoma are about 60-65%.
Treatment of pineoblastoma
Treatment for pineoblastoma depends on several factors including the size and location of the tumor and the child’s age. The main treatments for pineoblastoma are surgery, radiation therapy, and chemotherapy. Treatment plans are often similar to those used for medulloblastoma. Patients may be eligible for treatment through a clinical trial.
Surgery is used to remove as much of the tumor as possible. Surgery for pineoblastoma can be complex because of the tumor location and the risk to nearby blood vessels.
Some patients with pineoblastoma may have surgery to help manage hydrocephalus. This may include creating an opening in the floor of the third ventricle in the brain (third ventriculostomy) to keep fluid from building up. In other cases, doctors may place a shunt, a small tube that drains cerebrospinal fluid (CSF) so that the fluid can be removed from the brain. The shunt may be temporary or permanent.
Radiation therapy is often used after surgery for pineoblastoma. The dose and extent of radiation therapy depends on patient risk factors, whether the disease has spread, and patient age. Radiation is not used in very young children due to the increased risk of long-term side effects. In general, for patients older than 3 years of age, radiation is delivered over the entire central nervous system (craniospinal irradiation) with a higher dose (boost) at the primary tumor site. Late effects due to radiation can potentially occur and need to be monitored.
Chemotherapy is often used along with radiation therapy and surgery. Chemotherapy may be used before surgery to shrink the tumor to make it easier to remove or after surgery to kill cancer cells left behind. In very young children, chemotherapy may be used to help delay radiation until the child is older. A combination of chemotherapy medicines is used to treat pineoblastoma. These medicines often include vincristine, cyclophosphamide and cisplatin. Other types of chemotherapy may also be used.
Life after pineoblastoma
Ongoing follow-up care, laboratory tests, and routine MRI scans are used to monitor patients after completion of treatment. Monitoring should focus on early detection of recurrence and treatment for potential neurological, cognitive, and endocrine complications.
Patients who receive radiation therapy to the pineal gland are at risk for long-term endocrine problems including pituitary gland dysfunction (hypopituitarism). Low pituitary function can lead to problems such as delayed growth, fatigue, and fertility problems. Ongoing monitoring of hormone levels is important, and patients may need medicines including hormone replacement.
Regular checkups and screenings by a primary care physician are important to watch for health problems or late effects of treatment that can develop years after therapy.