Pineal Region Tumor
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A pineal region tumor is an abnormal growth in or near the pineal gland. Depending on the type of tumor, surgery may involve a craniotomy to remove it.
The pineal gland, a tiny, pinecone-shaped area located in the midline of the brain behind the third ventricle, synthesizes and secretes the neurotransmitters melatonin, which plays the critical role of regulating the body’s circadian rhythm, and serotonin, a precursor to melatonin. Other functions of the pineal gland remain incompletely understood. This gland is composed of a variety of cells, such as glial cells, endothelial cells, sympathetic nerve cells, pineal parenchymal cells. and germ cells. Given the diversity of cells, a wide variety of tumor types can arise in this region.
Germ cell tumors
Germ cell tumors develop from germ cells, which normally reside in the gonads and eventually become eggs or sperm. Most germ cell tumors are found in the gonads, but rarely—in about 2 to 3 percent of cases—these tumors arise outside of the gonads, most commonly in the brain. The reason for this is that during embryonic development, some germ cells accidently become trapped inside the developing brain, where they later develop into a tumor.
Intracranial germ cell tumors, which make up about one-third of pineal region tumors, are classified as germinomas and nongerminomatous, according to the World Health Organization. Germinomas are highly malignant and make up about half of intracranial germ cell tumors. Nongerminomatous tend to be malignant and more aggressive than germinomas and are further classified as choriocarcinomas, embryonal cell carcinomas, endodermal sinus tumors, mixed germ cell tumors and teratomas. Teratomas are broken down into immature teratomas, mature teratomas and teratomas with malignant transformation.
Pineal cell tumors
Unlike germ cell tumors, which arise in the pineal region despite being unrelated to the pineal gland itself, pineal cell tumors arise directly from the functional cells of the gland, pineal parenchymal cells, which are specialized nerve cells involved in processing visual stimuli. Pineal cell tumors are divided into pineocytoma, pineoblastoma, and mixed pineal tumors. Pineocytomas are generally slow-growing and benign, whereas pineoblastomas are aggressive and malignant. Mixed pineal tumors are a combination of pineocytoma and pineoblastoma.
Gliomas
Gliomas, namely astrocytomas and oligodendrogliomas, arise from glial cells and account for about one-third of pineal region tumors.
Meningiomas
Meningiomas in this region arise from arachnoid cells.
Other tumors
Other tumors, such as gangliogliomas and hemangioblastomas, can arise in this region, but constitute only a small portion of pineal region tumors.
Pineal cysts
Dermoid and epidermoid cysts are slow-growing sacs filled with material; they are not true tumors because they do not arise from brain tissue. Similar to germ cell tumors, these cysts are the result of cells being trapped in the brain during embryonic development. They are present at birth.
- Dermoid cysts arise from embryonic cells predestined to become skin and bones of the face and vertebrae; they contain a mixture of hair follicles, bone, cartilage and sebaceous glandular tissue.
- Epidermoid cysts arise from embryonic cells predestined to become skin; they contain mature skin tissue.
Symptoms
Regardless of the type, tumors in the pineal region usually cause symptoms through one of three mechanisms.
- Increasing pressure in the skull by blocking the flow of cerebrospinal fluid, leading to hydrocephalus
- Compressing part of the brain and surrounding structures
- Disrupting the endocrine system, which controls hormone production and secretion, including those hormones produced by the pineal gland
Hydrocephalus is a common symptom of tumors in this region and leads to headaches and possibly nausea, vomiting and altered mental status. The brainstem and the cerebellum are the most common sites of compression from a pineal region tumor and can cause abnormal eye movements (such as Parinaud syndrome), diplopia, ataxia or unsteady gait. Endocrine dysfunction is rare and usually is caused by hydrocephalus or the tumor spreading to the nearby hypothalamus.
Diagnosis
A neurological examination is usually performed to identify symptoms and any problems. This exam consists of evaluating eye movements, hearing, sensation, motor function, swallowing, sense of smell, balance, and coordination.
As with other brain tumors, imaging studies are the key component in the diagnosis of pineal region tumors. Magnetic resonance imaging (MRI) scans or computed tomography (CT) scans can be used to visualize the tumor and nearby structures in high detail. MRI scan, which can indicate the presence of hydrocephalus, is usually the preferred imaging test. MRI or CT scans may be performed with or without contrast enhancement.
A blood draw is performed to measure the biochemical markers alpha-fetoprotein and beta-human chorionic gonadotropin present in the blood, and a sample of cerebrospinal fluid may also be taken. Germ cell tumors can be differentiated by these biochemical markers.
Biopsy of the tumor may be needed to confirm a diagnosis and guide treatment decisions and can be done either before or during the surgical operation.
If the tumor is identified as malignant, an MRI scan of the spine will be performed to check for metastasis to the spine.
Risk Factors
The cause of pineal region tumors, like most brain tumors, is currently unknown.
Pineal region tumors are rare among adults, making up less than 1 percent of adult brain tumors, and are less rare among children, making up 3 to 8 percent of childhood brain tumors. For children, these tumors tend to occur between the ages of 10 and 20, and for adults, these tumors tend to occur after age 30.
Dermoid and epidermoid cysts can be present at birth and yet remain asymptomatic for years. Dermoid cysts tend to show symptoms in children younger than 10, and epidermoid cysts tend to show symptoms in middle-aged adults.
Treatments
At Columbia, our neurosurgeons use the latest surgical techniques to successfully treat pineal region tumors, providing patients with the best possible outcome.
For the majority of pineal region tumors, the standard first step of treatment is surgery. Historically, surgically removing a tumor from the pineal region of the brain has been a challenge because this is a hard-to-reach location. Advances have made surgery a successful treatment option.
Surgery involves a neurosurgeon performing a craniotomy, a procedure in which part of the skull is removed to gain access to the tumor, allowing the tumor to be excised. If hydrocephalus is present, a shunt may be placed before surgery.
The goal of surgery is always complete resection while also preserving nearby brain tissue and structures. For benign pineal region tumors, complete resection is usually achieved and often results in a cure, but for malignant pineal region tumors, complete resection is often not feasible without risking harm to surrounding tissue and instead the outcome is subtotal resection. Even subtotal resection is beneficial because it improves effectiveness of adjuvant treatment.
If tumor remains after surgery—as is often the case for malignant tumors—radiotherapy, chemotherapy or both may be used. For children younger than 3 years of age, radiotherapy is deferred until they are older because the radiation can interfere with their development. The neurosurgeon’s choice of radiotherapy or chemotherapy also depends on the type of tumor because some tumors tend to respond to one treatment better than others.
Radiotherapy is typically used for germ cell tumors, in particular germinomas because they respond particularly well to radiotherapy, and sometimes for pineoblastomas. Chemotherapy may be used for nongerminomatous and pineoblastomas after radiotherapy (or instead of radiotherapy for children younger than 3). The use of chemotherapy for treating pineal region tumors is limited because it has not been studied extensively.
Stereotactic radiosurgery, a noninvasive therapy in which a highly focused beam of radiation is used to target the cancer cells and leave the surrounding brain unaffected, may be used for small tumors, but this treatment option is not commonly used.
Pineal cysts that are asymptomatic typically do not require immediate treatment and can be observed over time.