Pineal Region Tumors (Germ cell tumors & Pineal parenchymal tumors)
Pineal region tumors represent a hetergenous group of lesions that arise in the region of the pineal gland, which is located behind the third ventricle at the top of the brainstem. The pineal gland produces several hormones including melatonin that regulates sleep-wake cycles. There are two primary categories of tumors that arise in the pineal region: germ cell tumors and pineal parenchymal tumors. In addition to these, the pineal region contains a variety of other cell types that are also found throughout the brain and tumors originating from these cells can also arise in the pineal region including: astrocytomas, meningiomas, ependymomas, metastatic brain tumors and epidermoid or dermoid cysts.
Germ cell tumors: These tumors commonly occur in the pineal region but can also near the pituitary gland in the suprasellar space. Germ cell tumors are thought to arise from the abnormal migration of cells in embryonic development during pregnancy. These tumors are not related to the pineal gland itself and can be benign (teratomas, dermoid and epidermoid tumors), malignant (germinomas, choriocarcinomas, endodermal sinus tumors and embryonal cell tumors) or mixed tumor types. These tumors are generally rare and usually manifest in patients by adolescence. Sometimes, biochemical markers in the blood and cerebrospinal fluid can differentiate the various tumor subtypes. This information is usually considered with imaging test results and biopsy to provide an accurate diagnosis and treatment plan.
Pineal parenchymal tumors: These tumors arise directly from pineocytes, cells of the pineal gland itself. These rare tumors can occur at any age and can be benign (Pineocytomas), malignant (Pineoblastomas) or have intermediate grade differentiation- meaning they share features of both malignant and benign tumors. Surgical biopsy results as well as imaging studies are used to provide an accurate diagnosis and assess the malignancy of these tumors in order to formulate a comprehensive treatment plan.
Symptoms
Symptoms, such as headache, nausea and vomiting, usually are the result of increased intracranial pressure from a backup of the cerebrospinal fluid that surrounds the brain and spinal cord. The backup of cerebrospinal fluid, called hydrocephalus, is very common with pineal tumors because they are located at the back of the third ventricle and block fluid flow into the sylvian aqueduct. As a pineal region tumor grows, it may interfere with the normal functions of the surrounding brain. In the pineal region, compression of the upper brainstem may lead to disruption of certain eye movements, including the inability to look up which is part of Parinaud’s syndrome. Other symptoms can include uncoordinated body movements and an unsteady gait.
Diagnosis
Pineal region tumors are diagnosed with a neurological examination followed by imaging studies of the brain, usually a computed tomography (CT) or magnetic resonance imaging (MRI) scan. The scan is usually performed with a contrast dye that makes the border and details of the tumor more visible in relation to the surrounding normal brain. The scan provides detail information regarding the presence of hydrocephalus, the exact size, location and probable type of tumor. However, only examination of a patient’s tumor tissue under a microscope can confirm an exact diagnosis. This tissue is usually obtained with either a biopsy or removal of the tumor. In some cases, neurosurgeons may employ a stereotactic MRI scan. In this study, a high-resolution contrast MRI is performed and a three-dimensional brain model is constructed using a computer system that is used to perform minimally invasive surgery and allow for volumetric three-dimensional removal of the tumor, which maximizes the degree of tumor removal. Depending on the type of tumor, an MRI entire spine and/or a lumbar puncture to sample cerebrospinal fluid may be performed to evaluate for the presence of any disseminated tumor cells within the spine and spinal fluid. This can play a role in determining the entire course of treatment after any surgery.
Treatment
In general the initial treatment for a pineal region tumor is usually surgical removal of the tumor. With modern techniques, surgery for a pineal region tumor is generally safe and allows the team at the Brain Tumor Center to obtain tumor tissue for accurate microscopic diagnosis and treatment planning. A number of surgical approaches to the pineal region exist which are tailored to the individual patient’s tumor and symptoms. Modern anesthetic and surgical advances allow for relatively safe surgery without the risks that were often associated with these procedures in the past. The use of microsurgical technique, intra-operative stereotactic navigation and endoscopic technology the likelihood of a complete removal is maximized and greater than ever before. If hydrocephalus is present, an endoscopic third ventriculostomy can often be performed to bypass the obstruction in the flow of cerebrospinal fluid. This is often preferred over the placement of a permanent shunt system (a tube with a regulating valve that allows spinal fluid to flow into the abdominal cavity), which is the alternative treatment for hydrocephalus. The endoscopic procedure avoids the potential risks associated with inserting a permanent shunt device and, often times, a minimally invasive biopsy of the tumor can be obtained during the same procedure.
For some benign tumors, complete resection is curative and is not followed by any other treatment. These patients are often observed with surveillance MRI studies to make sure there is no tumor recurrence. In other cases, such as with malignant tumors or tumors with intermediate differentiation surgery is often followed by chemotherapy or radiation therapy. In these cases maximal safe tumor removal is thought to improve the long-term outcome and response to treatment. Germinomas, for example, are particularly sensitive to radiation therapy while chemotherapy plays an important role in the other pineal region tumor types. Stereotactic radiosurgery, which involves delivery of a highly focused beam of radiation to the tumor that leaves the surrounding brain unaffected, can also be used in small tumors. After surgery, each patient is reviewed at our Multi-Disciplinary Tumor Board with an expert team of neuro-oncologists, medical oncologists, neuro-pathologists, neuro-radiologists and neurosurgeons. Together the tumor board recommends the best treatment options for each patient, incorporating ongoing national clinical trials and the latest treatment protocols.