Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia, Wikipedia.
PNETprimitive neuroectodermal tumor.
tumor(too'mor) [L. tumor, a swelling]
adenomatoid odontogenic tumorAdenoameloblastoma.
Neoplastic brain tumors may be benign or malignant. Malignant brain lesions may be primary or secondary, resulting from metastatic spread of other cancers. Primary malignant brain tumors make up from 10% to 30% of adult cancers and about 20% in children, but any of these tumors may occur at any age. Incidence in children is usually greatest before age 12, with astrocytomas, medulloblastomas, ependymomas, and brain stem gliomas being most common. In adults the most common tumors are gliomas and meningiomas, usually occurring supratentorially. Other malignant tumor types are oligodendrogliomas and acoustic neuromas (Schwannomas). Most malignant brain tumors are metastatic, with 20% to 40% of patients with cancer developing brain metastasis. The cause of primary brain cancers is unknown; however, one known environmental risk is exposure to ionizing radiation. Cell phone use has been implicated in acoustic neuromas. Central nervous system changes occur as the lesions invade and destroy tissue, and, because the tumors compress the brain, cranial nerves, and cerebral blood vessels, the compression causes cerebral edema and increased intracranial pressure (ICP). Most clinical signs are due to the increased ICP, but signs and symptoms may vary due to the type of tumor, its location, and the degree and speed of invasion. Usually the onset of symptoms is insidious, with brain tumors frequently misdiagnosed.
The patient is evaluated for neurological deficits (headache, mental activity changes, behavioral changes, weakness, sensory losses, or disturbances of vision, speech, gait, or balance). The patient is monitored for seizures and increased ICP. Diagnostic tools include skull x-rays, brain scan, CT scan, MRI, cerebral angiography, and EEG. Lumbar puncture demonstrates increased pressure and protein levels, decreased glucose levels, and (sometimes) tumor cells in the cerebrospinal fluid (CSF). Definitive diagnosis is by tissue biopsy performed by stereotactic surgery.
Treatment includes excision if the tumor is resectable, and size reduction if he tumor is not respectable; relieving cerebral edema, reducing ICP, and managing other symptoms; and preventing further neurologic damage. Treatment is determined by the tumor’s histology, radiosensitivity, and location. Functional MRI can map the brain function surrounding a tumor to help design a surgical approach that removes the tumor while avoiding damage to areas critical for normal functioning. Surgery, radiation, chemotherapy, and/or decompression for increased ICP with diuretics, corticosteroids, or sometimes ventroatrial or ventroperitoneal CSF shunting. Focused and computerized robotic radiation methods such as the Gamma Knife and Cyberknife permit delivery of more radiation to the tumor and less to surrounding normal tissue.
Radiation therapy can cause inflammation; therefore the patient is monitored for increasing ICP. If radiation is to be used after surgery, it will be delayed until the surgical wound has healed. However, even after local healing occurs, radiation can break down the wound; therefore the area of the incision must be assessed for infection and sinus formation. Chemotherapy for malignant brain tumors includes use of nitrosureas (BCNU, CCNU, procarbazine) to help break down the blood-brain barrier allowing entrance of other chemotherapy agents. Antiemetics are provided before and after chemotherapy to minimize nausea and prevent vomiting. The patient is assessed over the following weeks for bone marrow suppression, is advised to report signs of infection or bleeding, and is to avoid contact with crowds and people with respiratory infections. The oral agent temozolomide (Temodar) crosses the blood-brain barrier and is usually well tolerated by the patient. Intrathecal or intra-arterial administration helps increase drug action. Convection-enhanced delivery systems infuse the antitumor agent directly into the brain, bypassing the blood-brain barrier, to pump drugs slowly through 2 to 4 implanted catheters to where a tumor was removed, to attach to and kill remaining tumor cells, and to shrink a tumor before surgery. A disc-shaped drug wafer can be implanted during surgery to deliver chemotherapy directly to the tumor. MRI spectroscopy reveals the physiology of treated tumors to differentiate dead tissue from an actively growing tumor. The patient must be monitored closely for changes in neurologic status and increases in ICP. A patent airway must be maintained and respiratory changes monitored. The patient's safety must be ensured. Temperature must be monitored closely. Steroids and osmotic diuretics are administered as prescribed. Fluid intake may be restricted to 1500 ml/24 hr. Fluid and electrolyte balance is monitored to prevent dehydration. Stress ulcers may occur; therefore the patient is assessed for abdominal distention, pain, vomiting, and tarry stools. Stools are tested for occult blood. Antacids and anti-histamine-2 agents are administered as prescribed.
For postcraniotomy surgery, all general patient care concerns apply. General neurologic status and ICP remain the assessment priorities. Positioning of the patient after surgery depends on the procedure: after supratentorial craniotomy, the head of the bed should be elevated 30° and the patient positioned on the side to promote venous drainage, reduce cerebral edema, allow drainage of secretions and prevent aspiration. After infratentorial craniotomy, the patient should be kept flat for 48 hr but log-rolled side to side every 2 hr to minimize complications from immobility. Because brain tumors and their treatment frequently result in residual disabling neurologic deficits, a rehabilitation program should be started early. Physical and occupational therapists help the patient maintain independence and quality of life and provide aids for self-care and mobility. If the patient is aphasic or develops dysphagia, a speech pathologist must be consulted. Depression is common, and psychological consultation for behavioral or drug therapies may be helpful.
Emotional support is provided to the patient and family for treatments, disabilities, changes in lifestyle, and end-of-life issues. The patient and family are referred to resource and support services (e.g., social service, home health care agencies, the American Cancer Society, and other such voluntary agencies).
Brenner tumorSee: Brenner tumor
calcifying epithelial odontogenic tumorPindborg tumor.
carotid body tumor
connective tissue tumor
dysembryoplastic neuroepithelial tumorAbbreviation: DNET
Ewing tumorSee: Ewing tumor
fibroid tumorUterine leiomyoma.
follicular tumorAn epidermoid cyst.
giant cell tumor
giant cell tumor of bone
giant cell tumor of tendon sheath
granulosa cell tumor
granulosa-theca cell tumor
Gubler tumorSee: Gubler, Adolphe
Hürthle cell tumorSee: Hürthle, Karl W.
hilus cell tumor
islet cell tumor
Klatskin tumorSee: Klatskin tumor
Krukenberg tumorSee: Krukenberg, Friedrich Ernst
lipoid cell tumor of the ovary
mast cell tumor
melanotic neuroectodermal tumor
mesenchymal mixed tumor
Pancoast tumorSee: Pancoast tumor
placental site trophoblastic tumorAbbreviation: PSTT
Pindborg tumorSee: Pindborg tumor
primitive neuroectodermal tumorAbbreviation: PNET