Posterior Fossa Tumors 

Updated: Apr 03, 2018
Author: Hassan Ahmad Hassan Al-Shatoury, MD, PhD, MHPE; Chief Editor: Brian H Kopell, MD 

Overview

Practice Essentials

A brain tumor is one of the most devastating forms of human illness, especially when occurring in the posterior fossa. Brainstem compression, herniation, and death are all risks in tumors which occur in this critical location. Tumors in the posterior fossa are considered critical brain lesions, primarily because of the limited space within the posterior fossa and the potential involvement of vital brain stem nuclei. The clinical presentation depends on the site of the tumor, biological behavior and aggressiveness of the tumor, and the rate of growth. At the time of presentation, the patient may be very ill from severe headache or frequent vomiting due to associated hydrocephalus. Symptoms may be caused by focal compression of the cerebellum or brain stem centers and increased intracranial pressure.[1, 2, 3, 4]

No specific causes for posterior fossa tumors exist. However, genetic factors, such as dysfunction of some tumor suppressor genes (p53 gene) and activation of some oncogenes, may play a role in their development.[1] Environmental factors such as irradiation and toxins may also play a role.

Cushing probably was the first to report a large series of posterior fossa tumors. He published information about 61 patients with cerebellar medulloblastoma with mostly fatal outcome.[5]

Advances in brain surgery for tumors primarily were due to discovery of anesthesia, asepsis, neurologic localization, and the ability to achieve hemostasis. Hippocrates, who likely performed it for headache, epilepsy, fractures, and blindness, first described trephination.

An image depicting posterior fossa anatomy can be seen below.

Posterior fossa anatomy. Posterior fossa anatomy.

Posterior fossa tumors are more common in children than in adults. Central nervous system tumors are the most common solid tumors in children; between 54% and 70% of all childhood brain tumors originate in the posterior fossa.[6] About 15-20% of brain tumors in adults occur in the posterior fossa.

Certain types of posterior fossa tumors, such as medulloblastoma, pineoblastoma, ependymomas, primitive neuroectodermal tumors (PNETs), and astrocytomas of the cerebellum and brain stem, occur more frequently in children.Some glial tumors, such as mixed gliomas, are unique to children; they are located more frequently in the cerebellum (67%) and are usually benign.

Hydrocephalus is common in children with posterior fossa tumors, occurring in 71-90% of pediatric patients; approximately 10-40% demonstrate persistent hydrocephalus after posterior fossa tumor resection.[7, 8, 9, 10]

Patients older than 3 years are considered at standard risk or high risk and have long-term survival rates of approximately 85% and 70%, respectively. In patients 3 years or younger, survival rates are generally lower.[11]

Patients who present with posterior fossa tumors undergo surgery for the following goals[12, 13, 14, 15, 2, 16] :

  • To decompress the posterior fossa for the purpose of relieving pressure on the brain stem and/or to release intracranial pressure and avert the risk of herniation

  • To diagnose the tumor based on histopathology

  • To determine further plan of management depending on the nature of the tumor

  • When indicated, to treat hydrocephalus by shunting cerebrospinal fluid (CSF) to the peritoneal cavity (external CSF drainage or even no drainage is considered in some cases; still, many disagree regarding the ideal shunting procedure)[17, 9]

CT scan of the posterior fossa is inferior to MRI in diagnostic value because of the artifact produced from the surrounding thick bone. However, CT scan is helpful for postoperative follow-up. Cerebral angiography is useful to assess the vascular supply of the tumor, but with the wide availability of MRI, cerebral angiography is no longer used as the first option in brain tumor assessment.

Some patients should undergo an emergency operation, especially if they present with acute symptoms of brain stem involvement or herniation.[7, 8, 16, 18]  (See the images below.)

A 28-year-old female patient presented with headac A 28-year-old female patient presented with headache, ataxia, and blurring of vision. A T1-weighted MRI image, sagittal view, shows dilatation of the lateral ventricles.
A 28-year-old female patient presented with headac A 28-year-old female patient presented with headache, ataxia, and blurring of vision. A T1-weighted MRI image, sagittal view, shows an infratentorial mass with a large cystic component and small nodule. The mass is compressing the brainstem.
The tumor (the infratentorial mass) after excision The tumor (the infratentorial mass) after excision shows its vascular nature (see previous images).

Performing a lumbar puncture in patients with suspected posterior fossa tumors is contraindicated. A risk of central herniation exists even with a very small amount of CSF drainage. To avoid this catastrophe, a thorough clinical examination, including funduscopy and a CT scan of the brain should be performed before lumbar puncture.

Pathophysiology

Cerebellar astrocytoma

Cystic cerebellar astrocytoma comprises about 33% of all posterior fossa tumors in children. It represents 25% of all pediatric tumors. Average age at presentation is 9 years. Typically, cerebellar astrocytoma presents as a laterally located cyst with a well-defined solid component. The tumor may be solid or cystic and may be located medially in the vermis or laterally in the cerebellar hemisphere.

Primary neuroectodermal tumors

PNETs include medulloblastomas, medulloepitheliomas, pigmented medulloblastomas, ependymoblastomas, pineoblastomas, and cerebral neuroblastomas. These tumors originate from undifferentiated cells in the subependymal region in the fetal brain. PNETs are second to the cerebellar astrocytoma in frequency, comprising 25% of intracranial tumors in children.

Medulloblastoma

Medulloblastoma initially arises in the inferior medullary velum and grow to fill the fourth ventricle, infiltrating the surrounding structures. Some erroneously thought it arose from medulloblast cells, which do not exist. It is better included in the family of PNETs.[19]

Ependymoma and ependymoblastoma

Ependymomas are derived from ependymal cells. They occur more frequently in females, with 50% presenting in children younger than 3 years. An ependymoma has a much better prognosis than an anaplastic ependymoma (ependymoblastoma). Plastic ependymoma can mold itself to the available spaces inside or outside the ventricle without adhering to the ventricle.

Choroid plexus papilloma and carcinoma

Choroid plexus papilloma and carcinoma represent 0.4-0.6% of all intracranial tumors. They are more frequent in children than in adults (3% of childhood brain tumors). Sixty percent occur in the lateral ventricle and 30% in the fourth ventricle. The third ventricle and cerebellopontine angle are rare locations for this tumor. Cerebrospinal fluid (CSF) overproduction may occur, sometimes reaching more than 4 times normal volumes. In most of cases, CSF analysis demonstrates increased protein, xanthochromia, or both.

Dermoid tumors

Dermoid tumors arise from incomplete separation of epithelial ectoderm from neuroectoderm at the region of the anterior neuropore; this usually occurs during the fourth week of gestation. The cyst wall often includes hair follicles, sweat glands, and sebaceous glands. The cyst grows slowly and gradually becomes filled by desquamated epithelium, sweat, and sebaceous materials. Aseptic meningitis is a sequela of cyst rupture. More commonly, the cyst occurs in the posterior fossa, at or near the midline. It may be extradural, vermian, or intraventricular. A dermal sinus may be connected to the mass. It may be detected clinically or by MRI.

Hemangioblastoma

Hemangioblastoma represents about 7-12% of all posterior fossa tumors. About 70% of hemangioblastomas occurring in the cerebellum are cystic. Age of presentation is 30-40 years old. Hemangioblastomas are more common in males. Hemangioblastoma may be associated with von Hippel-Lindau disease.[20]

Metastatic tumors

Three percent of all cranial metastatic lesions occur in the brainstem, and 18% occur in the cerebellum. Originating sites include breast, lung, skin, and kidney. Solitary metastasis is better treated by surgical removal before radiation therapy. Surgery also should be considered in case of radiosensitive original tumors or when the primary source is unknown.

Brainstem gliomas

Brainstem gliomas constitute 15% of all brain tumors. In children, brainstem glioma represents 25-30% of all brain tumors. Most brainstem gliomas are low-grade astrocytoma.

Relevant Anatomy

The posterior cranial fossa is the deepest and most capacious of the 3 cranial fossae. It contains the cerebellum, pons, and medulla oblongata. The foramen magnum is located centrally and inferiorly in the posterior fossa. The posterior fossa is surrounded by deep grooves containing the transverse sinuses and sigmoid sinuses.

The brainstem is the portion of the brain connecting the cerebral hemispheres with the spinal cord. It contains the midbrain, pons, and medulla oblongata. The brainstem is partially obscured by the cerebral hemispheres and cerebellum. The gray matter in the brainstem is scattered into numerous small masses called nuclei, many of which are motor or sensory nuclei of the cranial nerves.

The midbrain is the portion of the brain that connects the pons and the cerebral hemispheres. The dorsal segment of the midbrain is called the tectum; the more central and ventral portion is called the tegmentum.

The pons lies anterior to the cerebellum and superior to the medulla, from which it is separated by a groove through which the abducens, facial, and acoustic nerves emerge.

The medulla oblongata is the pyramid-shaped segment of brainstem between the spinal cord and pons. The lower half contains the remnants of the central canal; the posterior portion of the superior half forms the floor of the body of the fourth ventricle.

The cerebellum is located in the posterior fossa of the skull, dorsal to the pons and medulla. It is separated from the overlying cerebrum by an extension of dura mater, the tentorium cerebelli. It is oval in form, with its widest diameter along the transverse axis. It is composed of a small, unpaired central portion (the vermis) and 2 large lateral masses (the cerebellar hemispheres).

Prognosis

The 5-year survival rates exceed 60% for all patients and 80% for certain good-risk individuals with posterior fossa tumors. In cases of pilocytic cerebellar astrocytoma, the 25-year survival rate exceeds 94%.[21]

Patients with medulloblastoma are classified into good-risk and bad-risk categories based on the following:

  • Age of presentation
  • Extension of surgical resection
  • Leptomeningeal dissemination or metastasis

Prognosis in medulloblastoma is worse for children younger than 2 years, for patients with subtotal resection (80%), and for those with subarachnoid metastasis or positive results on CSF cytology more than 2 weeks after surgery. In patients with ependymomas, the 5-year survival rate is 20%; in ependymoblastoma, the 5-year survival rate is only 6%.

Choroid plexus papilloma has excellent prognosis, as high as 100% survival rate. Choroid plexus carcinoma has a poor prognosis.

 

Presentation

History

The clinical presentation depends on the site of the tumor, biological behavior and aggressiveness of the tumor, and the rate of growth. At the time of presentation, the patient may be very ill from severe headache or frequent vomiting due to associated hydrocephalus.

Symptoms may be caused by focal compression of the cerebellum or brain stem centers and increased intracranial pressure.

Symptoms due to focal brainstem compression include cranial nerve dysfunction, which  commonly involves the nuclei or tracts of the third, fourth, or sixth cranial nerves, resulting in ocular palsies and diplopia and long tract signs (hemiparesis).

Symptoms due to focal compression of the cerebellum include characteristic eye findings and vermian syndrome. Truncal ataxia is a common finding in midline tumors, such as medulloblastomas, ependymomas, and vermian astrocytomas. It is manifested by a tendency to fall frequently and a widely based gait.

Hemi-cerebellar syndrome involves limb ataxia, nystagmus, and dysmetria. Tumors that occur in the cerebellar hemisphere, such as metastases, cerebellar astrocytomas, or cystic hemangioblastomas, may present by ataxia of the contralateral limbs. Nystagmus usually occurs late in the disease. Vertical nystagmus suggests a lesion in the anterior vermis, periaqueductal region, or craniocervical junction. Horizontal nystagmus implies involvement of the cerebellar hemisphere.

Intracranial hypertension causes the following 8 symptoms:

  • Headache  is the most common symptom in patients with posterior fossa tumors. Associated neck pain, stiffness, or head tilt suggest tonsillar herniation into the foramen magnum. Headache is insidious and intermittent. It is most severe in the morning or after a nap because of increased intracranial pressure from recumbency and hypoventilation during sleep. Headache manifests in children as irritability and difficulty to be handled.

  • Vomiting may be due to generalized intracranial hypertension or irritation of the vagal nuclei in the medulla oblongata or area postrema of the fourth ventricle; it usually occurs in the morning. Vomiting sometimes relieves headache.

  • Strabismus is secondary to sixth nerve palsies from intracranial hypertension. Third nerve palsies may also occur.

  • Blurring of vision due to papilledema

  • Meningismus

  • Dizziness

  • Macrocephaly in children

  • Hydrocephalus

Young age, moderate to severe hydrocephalus, transependymal edema, the presence of cerebral metastases, and tumor pathology (medulloblastoma and ependymoma) on presentation may predict postresection or persistent hydrocephalus.[7]

 

Workup

Laboratory Studies

Lab studies include the following:

  • Complete blood profile: Used for preoperative preparation, and as a diagnostic tool in some patients. In cases of hemangioblastoma, erythrocytosis may be found, presumably from erythropoietic factors secreted by the tumor.

  • Coagulation profile

  • Blood grouping

  • Renal function tests

  • Liver function tests

  • Tumor markers

    • A tumor marker is any substance that makes possible either a qualitative diagnosis of neoplasm or a quantitative estimate of tumor burden.

    • They are used for screening, for staging, and for evaluation of response to therapy and detection of early tumor recurrence.

    • Three examples of tumor markers include (1) carcinoembryonic antigen (CEA), (2) alpha-fetoprotein (AFP), and (3) placental proteins.

    • The diagnostic role of tumor markers is less crucial in the posterior cranial fossa than in other regions of the body because of the ability of MRI to clearly visualize distinctive characteristics, such as cysts.

Imaging Studies

Imaging modalities include the following:

  • Plain x-ray skull: May show signs of chronic intracranial hypertension; may show calcification; in case of a dermoid cyst, a bone defect with sclerotic margins may be detected.

  • CT scanning: CT scan of the posterior fossa is inferior to MRI in diagnostic value because of the artifact produced from the surrounding thick bone. However, CT scan is helpful for postoperative follow-up.

  • Cerebral angiography: Useful to assess the vascular supply of the tumor; with the wide availability of MRI, cerebral angiography is no longer used as the first option in brain tumor assessment.

  • Magnetic resonance imaging[22, 23, 24, 25]

    • Cerebellar astrocytoma:

      • Intra-axial, either midline or hemispheric, mass

      • Prominent cystic component that is hypointense in T1-weighted images and slightly hyperintense in T2-weighted images (more protein content)

      • Mural nodule, usually enhanced in T2 images

      • Displacement of effacement of the fourth ventricle

      • Hydrocephalic changes due to obstruction of the CSF pathway

      • Nodule that usually is enhanced with contrast

      • Cystic wall that may or may not enhance

      • Heterogenicity and calcification, rarely found

    • PNET:

      • Intraventricular midline or paramedian mass that is isointense in T1 images

      • Prominent enhancement with intravenous contrast

      • May appear heterogeneous on MRI, with areas of cystic degeneration and central necrosis

      • Infrequently, calcification, eccentric location, and lack of enhancement

    • Ependymomas:

      • Commonly found intraventricularly

      • Calcification found in 45% of cases

      • Plastic ependymomas that can extend through the foramina of Magendie and Luschka to compress the craniocervical junction and/or the brain stem

      • Extension to the cerebellopontine angle that is pathognomonic of ependymomas

      • Enhance with intravenous contrast

      • May be heterogeneous in character

    • Fossa hemangioblastoma:

      • Appears as a cystic mass with pial-based mural nodule that is slightly hyperintense and enhanced prominently with intravenous contrast

      • Appearing as regions of signal void on spin-echo images, abnormal vessels that may be found adjacent or within the tumor

      • Cyst that may be isointense or hyperintense on T1- and T2-weighted images

      • Cyst wall that often is sharply delimited

      • Variation of MRI appearance, including presence of hemorrhage in the cyst, solid rather than cystic mass, multiple lesions, and associated syrinx cavity

    • Posterior fossa choroids plexus papilloma:

      • Intraventricular mass with lobulated margin

      • Hypointense on T1 images

      • Patchy regions of hypointensity that express calcification and hypervascularity

      • Region of hyperintensity on T2 images (calcification and old hemorrhage)

      • Prominent enhancement with intravenous contrast

      • Tumor extension through foramina of Luschka or Magendie into the basal cisterns

      • Commonly, hydrocephalic changes

    • Fossa dermoid cyst:

      • Hyperintense on T1 images and hypointense on T2 images

MRI is a helpful postoperative tool to detect early recurrence before it is manifested clinically. The interval of MRI scanning depends on the tumor histology and postoperative course. Patients receiving chemotherapy for a malignant lesion also should be studied between chemotherapy cycles to assess response. The presence of residual or recurrent contrast enhancement 2 months after surgery suggests recurrence. Postirradiation changes may mimic recurrence, requiring follow-up after few weeks. 

Othman and Abdullah suggest that serial quantitative MRI may be able to predict patients at risk of developing neurocognitive impairment following chemoradiotherapy for posterior fossa tumors by identifying lower hippocampal volumes and altered hippocampal growth trajectory.[26]

Dynamic susceptibillity contrast perfusion MRI has been shown to  help identify posterior fossa tumors such as pilocytic astrocytoma, ependymoma, and medulloblastoma by identifying significant differences in relative corrected cerebral blood volume, relative quantifications of cerebral blood flow, and permeability indices.[22]

In one study, thallium-201-SPECT was combined with FDG-PET for differential diagnosis of posterior fossa brain tumors using multiple discriminant analysis. Hemangioblastoma, low-grade glioma, and malignant lymphoma were well discriminated, but anaplastic astrocytoma, glioblastoma, medullobastoma, and metastatic tumors could not be well distinguished.[27]

Brainstem auditory evoked response (BAER) specifically is helpful as an intraoperative monitor of brainstem function. Abnormal response alerts the surgeon about potential danger that, in most cases, can be reversed early.

Histologic Findings

Cerebellar astrocytoma:

  • Pilocytic subtype (61%): Most astrocytes found in the tumor are fibrillary, with round-to-oval nuclei with some cytoplasmic pleomorphism and Rosenthal fibers. A honeycomb pattern (area with densely and areas with loosely cellular appearance) is present. Malignant transformation is uncommon.

  • Infiltrative fibrillary type (28%): It usually occurs in adults. It displays the histologic features of anaplasia.

Anaplastic astrocytoma (11%):

  • More anaplastic features are present.

Medulloblastoma

See the list below:

  • Grossly, it appears as a soft and friable mass. Area of necrosis and focal hemorrhage may be present.

  • Calcification is uncommon.

  • The tumor may infiltrate the brainstem and adjacent cerebellar structures in 30% of patients.

  • Dissemination through the subarachnoid space is common. Metastatic lesions are present in 50% of patients at autopsy.

  • The tumor appears highly cellular with round-to-oval cells.

  • Cytoplasm is scant, and hyperchromic nuclei are present. With hematoxylin and eosin staining, it appears as a blue tumor.

  • Homer-Wright rosettes and pseudorosettes are commonly present, suggesting neuronal differentiation.

Ependymomas (3 classic histologic features)

See the list below:

  • Uniform-appearing cells are arranged around a vessel, forming perivascular pseudorosettes.

  • A true ependymal rosette is present.

  • Cells contain blepharoplasts (basal bodies of cilia).

Ependymoblastoma (histologic features of malignancy)

See the list below:

  • Cytoplasmic and nuclear pleomorphisms are present.

  • Nuclear hyperchromatism occurs.

  • Excessive mitosis occurs.

  • Necrosis is present.

  • Cytoarchitectural disorganization is present.

Choroid plexus papilloma

See the list below:

  • Gross picture: It is a reddish mass with an irregular surface.

  • Microscopic picture: Cuboidal epithelial cells similar to the normal choroids plexus are present.

Hemangioblastoma

See the list below:

  • Macroscopic picture: Yellow to pink in color. The mural nodule is found touching the pial surface of the cerebellum. In 20% of cases, the dura is involved. The cystic wall and its contents may be yellow or white.

  • Microscopic picture: Benign cellular proliferation, with formation of vascular channels, occurs. Reticulin-rich stromal network and (fat-laden) cells are characteristic.

 

Treatment

Approach Considerations

No primary medical therapy exists for posterior fossa brain tumors. Medications, such as Lasix and corticosteroids, are administered before surgery to reduce the effect of edema on the surrounding structures.

Some patients should undergo an emergency operation, especially if they present with acute symptoms of brain stem involvement or herniation. The most common operative approaches to the posterior fossa tumors are midline, paramedian, or retromastoid.

Preoperative Details

Preoperative details include the following:

  • Assessment of the general condition of the patient.

  • Preoperative clearance, including cardiovascular assessment, pulmonary assessment, renal assessment, metabolic assessment, and hematologic assessment.

  • Management of the secondary effects of tumor and intracranial hypertension, such as headache, vomiting, and dehydration.

  • Reservation of at least 3 units of fresh blood in case of intraoperative need.

  • Managing symptomatic obstructive hydrocephalus before surgical removal of the tumor (2 schools of thought).

  • CSF shunting, either internal or external (may expose the patient to the additional inherent shunt risks as well as infection or other surgical complications).

  • Medical management - Decreasing the intracranial pressure by administering glucocorticoids, such as dexamethasone in a dose of 1 mg/kg/day.

  • Neurologic deterioration - Possible emergent operation for tumor removal.

Intraoperative Details

Operative position

Prone is comfortable for the surgeon. The head is fixed in 3-point head fixation if the patient is older than 2 years.[28]

The sitting position carries the risk of air embolism. It is less comfortable for the surgeon. The field is much clearer because drainage is easier. In children younger than 2 years, a Mayfield headrest is used. The head is flexed slightly, without compressing the neck vessels.

Safety burr hole

A safety burr hole is placed in the occipital area. This could be used in case of acute hydrocephalus requiring ventricular drainage.

In patients with hydrocephalus, the ventricle is cannulated through this burr hole. The catheter is tunneled subcutaneously and connected to an external ventricular drainage system for subsequent management.

General operative principles

Midline incision extends from the inion to the upper cervical vertebra.

The paracervical and suboccipital muscles are separated by diathermy.

Craniectomy is performed according to the site and size of the tumor.

The foramen magnum is opened, and the C1 arch may be removed, especially in tumors extending to, or beyond, the craniocervical junction.

The dura is opened in Y-shape, with the base upward.

Bipolar and self-retaining retractors are used for cerebellar cortical incision to expose the tumor.

Tumors are removed using gentle suction, ultrasonic surgical aspirator, or carbon dioxide laser. The last method is used only infrequently.

The extent of tumor removal should be weighed with the possible risk of complication, especially with tumors adherent to the brainstem.

The dura is closed in a watertight fashion. Dural grafting may be needed for complete closure.

Using an Ommaya reservoir for perioperative external ventricular CSF drainage enabled tumors to be wholly and safely removed. Restoring CSF circulation provided an effective means of controlling and preventing hydrocephalus secondary to posterior fossa tumors in children.[29]

Special concerns

Choroid plexus papilloma should be removed totally because it is a benign tumor that does not invade the brain.

If a dermoid cyst is associated with a sinus, the sinus should be removed completely.

Postoperative Details

Early postoperative care includes the following:

  • Increased ataxia.

  • Increased lower cranial nerve dysfunction.

  • Apnea, or respiratory abnormalities.

Late postoperative care includes the following:

  • Medulloblastoma: Adjuvant therapy should be administered in medulloblastoma. In this type of tumor, both the brain and spinal cord receive radiation therapy.

  • Adjuvant chemotherapy is also administered in poor-risk patients with medulloblastoma in the form of cyclophosphamide-cisplatin-vincristine.[30]

  • Ependymomas: In cases with ependymomas, craniospinal irradiation should be considered because subarachnoid seeding sometimes is found, especially in the anaplastic type and those in the fourth ventricle. Recurrent cases may be administered adjuvant chemotherapy as bischloroethylnitrosourea (BCNU) and dibromodulcitol.[31]

  • Choroid plexus papilloma and carcinoma: Seeding of tumor cells in the subarachnoid space has been reported, although it is uncommon. Radiation therapy for this metastasis is still under research.

  • Hemangioblastoma: Complete surgical resection should be the aim of surgery. However, in case of subtotal removal, radiation therapy may be useful to eradicate the residual tumor.

Complications

Possible complications of posterior fossa tumor surgery include the following:

  • Lower cranial nerve dysfunction

  • Facial nerve palsy

  • Deafness[32]

  • Long tract deficits

  • Hemiplegia

  • Hemiparesis

  • Sensory abnormalities

  • Other postoperative complications

  • Infection

  • Prolonged coma

  • Shunt obstruction or malfunction

  • Chest infection

  • Deep venous thrombosis

  • Pulmonary embolism

  • Cerebrospinal fluid leak

  • Ocular motor abnormalities[33]

  • Cerebellar mutism syndrome[34, 35]

Future and Controversies

Future management

Stereotactic radiosurgery utilizes only the physical properties of the irradiation to deliver deadly radiation doses to the tumor. Stereotactic radiotherapy benefits from the differences in radiobiological properties between normal and pathological tissue.[12, 13]

In interstitial brachytherapy, a radioactive material is implanted into the tumor bed at the time of surgery to deliver a continuous, localized dose of irradiation. Chemotherapy with new therapeutic medications may have a role in the treatment of residual tumors after surgery.

Immunotherapy aims at activation of cell-mediated cytotoxic responses and humorally mediated cytotoxic response against the tumor cells. This is still investigational.

Special issues

An informed consent must be obtained from the patient if his or her general condition permits understanding the risks and potential benefits of surgery; otherwise, it must be obtained from relatives. The discussion related to the informed consent should include the following:

  • Summary of the nature of the condition and its presumed course without treatment

  • Description of the proposed surgical treatment

  • Possible complications that can occur as a result of surgery

  • Review of alternative treatment modalities, including a brief discussion of the pros and cons of each treatment

  • A statement that the operation is not guaranteed to improve the patient's condition