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primitive neuroectodermal tumor.


(too'mor) [L. tumor, a swelling]
1. A swelling or enlargement; one of the four classic signs of inflammation.
2. An abnormal mass. Growth or proliferation that is independent of neighboring tissues is a hallmark of all tumors, benign and malignant. Synonym: neoplasm See: cancer

adenomatoid odontogenic tumor

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brain tumor

An inexact term to describe any intracranial mass: neoplastic, cystic, inflammatory (abscess), or syphilitic.

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.

Patient care

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 tumor

See: Brenner tumor

brown tumor

A benign fibrotic mass found within the bone of patients with unchecked hyperparathyroidism. The tumor appears brown on gross examination because it contains blood and by-products of the metabolism of hemoglobin.

Buschke-Loewenstein tumor

A giant condyloma acuminatum, typically found on the genitals or anus, caused by infection with papilloma virus. In men, it is almost always found under the foreskin (it is rarely reported in circumcised men). It may transform into a verrucous carcinoma and cause deep local tissue invasion.

calcifying epithelial odontogenic tumor

Pindborg tumor.

carotid body tumor

A benign tumor of the carotid body.

collision tumor

1. A malignant growth made up of two or more different cell types occurring simultaneously in the same location.
2. A cancerous growth made up of two or more malignancies that have metastasized toward each other.

connective tissue tumor

Any tumor of connective tissue such as fibroma, lipoma, chondroma, or sarcoma.

Dapaong tumor

A painful, nodular mass in the large bowel, a result of infection with Oesophagostomum bifurcum, a West African worm.

desmoid tumor

A tumor of fibrous connective tissue.
Synonym: desmoma

dysembryoplastic neuroepithelial tumor

Abbreviation: DNET
A benign mass of misshapen brain cells. DNETs are a relatively rare cause of seizures in children and adolescents.

endocrine-inactive tumor

A pituitary adenoma that does not secrete a clinically important concentration of hormones. Endocrine-inactive tumors were formerly known as chromophobe adenomas. They are the most commonly detected neoplasms of the pituitary gland.

erectile tumor

A tumor composed of erectile tissue.

Ewing tumor

See: Ewing tumor

false tumor

An enlargement due to hemorrhage into tissue or extravasation of fluid into a space, rather than cancer.

fibroid tumor

Uterine leiomyoma.

follicular tumor

An epidermoid cyst.

functioning tumor

A tumor that is able to synthesize the same product as the normal tissues from which it arises, esp. an endocrine or nonendocrine tumor that produces hormones.

giant cell tumor

1. A malignant or benign bone tumor that probably arises from connective tissue of the bone marrow. Histologically, it contains a vascular reticulum of stromal cells and multinucleated giant cells.
2. A yellow giant cell tumor of a tendon sheath.
3. Epulis.
4. A chondroblastoma.

giant cell tumor of bone

A benign or malignant tumor of bone in which the cells are multinucleated and surrounded by cellular spindle cell stroma.

giant cell tumor of tendon sheath

A localized nodular tenosynovitis.

granulosa cell tumor

A malignant tumor that arises from the supporting cells (stromal cells) that encircle the ovary. Many of these cells produce estrogen; those that do can cause breast tenderness, endometrial hyperplasia, menorrhagia, or, in children, sexual precocity.

granulosa-theca cell tumor

An estrogen-secreting tumor of the ovary made up of either granulosa or theca cells.

Gubler tumor

See: Gubler, Adolphe

heterologous tumor

A tumor in which the tissue differs from that in which it is growing.

homologous tumor

A tumor in which the tissue resembles that in which it is growing.

Hürthle cell tumor

See: Hürthle, Karl W.

hilus cell tumor

A rare, steroid-hormone–producing tumor of the ovary. It is an occasional cause of virilization.

islet cell tumor

A tumor of the islets of Langerhans of the pancreas.

Klatskin tumor

See: Klatskin tumor

Krukenberg tumor

See: Krukenberg, Friedrich Ernst

lipoid cell tumor of the ovary

A masculinizing tumor of the ovary. It may be malignant.

mast cell tumor

A benign nodular accumulation of mast cells.

melanotic neuroectodermal tumor

A benign tumor of the jaw, occurring mostly during the first year of life.

mesenchymal mixed tumor

A tumor composed of tissue that resembles mesenchymal cells.

milk tumor

A colloquial term for a galactocele.
Synonym: galactocele (1) See: caked breast

Pancoast tumor

See: Pancoast tumor

papillary tumor

A neoplasm composed of or resembling enlarged papillae.
See: papilloma

phantom tumor

1. An apparent tumor due to muscular contractions or flatus that resolves on reexamination of the patient.
2. A mass that resembles a tumor in only one view of a chest x-ray film. On other views it either disappears or appears to be an encapsulated fluid collection.

placental site trophoblastic tumor

Abbreviation: PSTT
A rare form of gestational trophoblastic disease simulating carcinoma and arising at the attachment of the placenta to the uterine wall.

Pindborg tumor

See: Pindborg tumor

primary tumor

In a patient with metastatic cancer, the lesion assumed to be the source of the metastases.

primitive neuroectodermal tumor

Abbreviation: PNET

Recklinghausen tumor

See: Recklinghausen, Friedrich D. von

sand tumor


secondary tumor

A tumor that has formed at a location remote from the original location of the tumor. Generally, a secondary tumor results from the spread of malignant cells through the lymphatic system or bloodstream.

teratoid tumor

A tumor of embryonic remains from all germinal layers. See: teratoma

turban tumor

Multiple cutaneous cylindromata that cover the scalp like a turban.

uterine tumor

, tumor of the uterus
Uterine neoplasia, which may cause sterility or abortion or obstruct labor. Uterine tumors may become infected or twisted on their attachments. See: cancer of uterus; endometrioma; uterine fibroma

vascular tumor


Warthin tumor

See: Warthin tumor

Wilms tumor

See: Wilms tumor
References in periodicals archive ?
The time to presentation of these secondary tumors was calculated by Sobowale to be an average of ten years after radiation, and the age of presentation for these tumors significantly higher than that for primary PNETs, with a mean presentation age of seventeen years.
The cytologic differential diagnosis of PNET includes lymphoma, neuroblastoma, embryonal rhabdomyosarcoma, small cell carcinoma, synovial sarcoma, small cell variant of melanoma, basaloid squamous cell carcinoma and poorly differentiated non keratinized squamous cell carcinoma (13-18).
12,13] Renal PNET is treated with similar chemotherapeutic agents used with Ewing's sarcoma given their biologic similarities.
12) Patients with renal PNET may present with malaise, an increase in abdominal circumference, weight loss, nephric colic, fever, flank pain, hematuria, and night sweats.
These electron microscopic findings were also consistent with a PNET.
Renal PNET is extremely rare with fewer than 50 cases in the English literature.
The results indicate that the diagnoses of MB, AT/RT, and PNET are valid and reproducible as determined by a 2 out of 3 consensus being at least 95%.
Examples of this include ES/ PNET (with the various translocation partners adjoined to EWSR1) and myxoid/round cell liposarcoma.
The approval has been particularly important as there are no therapies currently available that can significantly delay tumor growth and improve the progressionfree survival of patients with advanced PNET, and as a result this drug has been eagerly anticipated.
Sunitinib, marketed by Pfizer under the brand name Sutent([R]), is an oral, small molecule angiogenesis inhibitor that is currently approved for the treatment of RCC, GIST and PNET.
118,119) These are typically pediatric tumors and include medulloblastoma, supratentorial "central" PNET, medulloepithelioma, ependymoblastoma, and atypical teratoid rhabdoid tumor (AT/RT).
The researchers found that taking multivitamins later in pregnancy did not significantly reduce the child's risk of medulloblastoma and PNET.