Astrocytoma overview
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Astrocytoma overview On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Astrocytomas are primary intracranial tumors derived from astrocytes cells of the brain. They may arise in the cerebral hemispheres, in the posterior fossa, in the optic nerve, and rarely, the spinal cord. Astrocytomas are a type of neoplasm of the brain. They originate in a particular kind of glial-cells, star-shaped brain cells in the cerebrum called astrocytes. This type of tumor does not usually spread outside the brain and spinal cord and it does not usually affect other organs. Astrocytomas are the most common glioma and can occur in most parts of the brain and occasionally in the spinal cord.
Historical Perspective
Astrocytoma was first described by Virchow in 1840 as glioma duram. In 1932, the histological description of cerebellar astrocytoma was given by Bergstrand.
Classification
Astrocytoma may be classified according to its histology into 4 grades: pilocytic astrocytoma, diffuse astrocytoma, anaplastic astrocytoma and glioblastoma multiforme.
Pathophysiology
On gross pathology, compression, invasion and destruction of brain parenchyma are characteristic findings of astrocytoma. On microscopic histopathological analysis, gemistocytes, rosenthal fibres and hyalinisation of blood vessels are characteristic findings of astrocytoma.
Causes
The cause of astrocytoma has not been identified.
Differential Diagnosis
Astrocytoma must be differentiated from other space occupying CNS lesions that cause neurological symptoms such as subependymal nodule, central neurocytoma, oligodendroglioma, intraventricular meningioma, intraventricular metastasis, medulloblastoma, sarcoma, primitive neuroectodermal tumor, choroid plexus carcinoma and glioblastoma multiforme.
Epidemiology and Demographics
In 2014 the incidence of pilocytic astrocytoma is 0.23 per 100,000 and the number of new cases is 700 per year in United States. Patients of all age groups may develop astrocytoma. Pilocytic astrocytoma accounts for 0.6-5.1% of all intracranial neoplasms.
Risk Factors
Common risk factors in the development of astrocytoma are past exposure to radiation therapy to the brain and congenital diseases.
Natural History
If left untreated, low grade astrocytoma associated with epilepsy is less malignant over time and has lower level of recurrence. Common complications are increased intracranial pressure, cognitive dysfunction, behavioral complications, vision defects and muscle weakness. Low grade astrocytoma and isolated tumor have a better prognosis than high grade astrocytoma and diffuse tumor.
History and Symptoms
If left untreated, low grade astrocytoma associated with epilepsy is less malignant over time and has lower level of recurrence. Common complications are increased intracranial pressure, cognitive dysfunction, behavioral complications, vision defects and muscle weakness. Low grade astrocytoma and isolated tumor have a better prognosis than high grade astrocytoma and diffuse tumor.
Physical Examination
The patients with astrocytoma usually appear alert and awake. The signs depend on the location of tumor. Physical examination of patients with astrocytoma is usually remarkable with signs of trunkal ataxia, papilledema, nystagmus and abducens nerve palsy.
Laboratory Findings
There are no diagnostic lab findings associated with astrocytoma.
CT
On cranial CT, astrocytoma is characterized by isodense or hypodense regions of positive mass effect, often without any enhancement. Calcification and either cystic or fluid attenuation components are also encountered in CT depending on the type and grade of the tumor.
MRI
On MRI of head, astrocytoma is characterized by non-enhancing isointense to hypointense lesions compared to white matter.
Biopsy
Tumor biopsy findings associated with astrocytoma include microcystic tumor matrix, gemistocytes, rosenthal fibres and hyalinization of blood vessels. High grade tumors are characterized by high cellularity, pleomorphism, nuclear atypia, increased mitotic activity, necrosis and microvascular proliferation.
Medical Therapy
The optimal therapy for astrocytoma depends on the stage at diagnosis. Chemotherapy is recommended for children. Radiation and chemotherapy with stem cell transplant is recommended for adults with high grade astrocytoma.
Surgery
Surgery is the mainstay of treatment for certain types of astrocytoma such as glioblastoma multiforme. The feasibility of surgery depends on the stage of astrocytoma at diagnosis.