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ASTROCYTOMA

An Astrocytoma is a tumor that arises from Astrocytes which are the most numerous of the different types of Glial Cells. Glial cells have an enormous potential for abnormal growth and are the chief source of CNS tumors. Approximately half (1/2) of all Primary Brain Tumors are Glial cell neoplasms (tumors) and more than three quarters (3/4) of all Gliomas are Astrocytomas which, themselves, are a heterogeneous group of tumors that are grouped by grades.

SYMPTOMS

The first symptom of a Brain Tumor of any type can be a headache, caused by increased pressure in the Brain and therefore, inside the Skull. The headache associated with a Brain tumor, is frequently worse in the morning, frequently accompanied by vomiting. Other symptoms of a Brain tumor can include seizures (Epilepsy), weakness or numbness of a side or part of the body, or subtle symptoms such as changes in mood, thinking or general state of well being. Increased intracranial pressure can cause blurred, double or lost vision.

A FIRST SEIZURE (EPILEPSY), IN ANYONE OVER THE AGE OF 21 IS CONSIDERED TO BE DUE TO A BRAIN TUMOR UNTIL PROVEN OTHERWISE.

DIAGNOSIS

If a patient has any of the above symptoms without any obvious explanation, further work-up is warranted. These tumors can be best seen by Magnetic Resonance Imaging (MRI). CT scans can also be used; however, the quality of Brain and tumor substance detail is best provided by MRI.


Figure 1A (Left): MRI Scan (Transaxial View-Gadolinium Enhanced) of a 3rd Ventricular Glioma (Arrow). The tumor has obstructed the normal CSF pathways resulting in Hydrocephalus.

Figure 1B (Right): MRI Scan (Sagittal View-same patient.) This is a "solid" tumor that partially "enhances" (Arrow.)


Need to Establish the Precise Pathology

Once a mass is confirmed by any of the neuroimaging techniques, the diagnosis needs to be established by a biopsy of the mass. The biopsy, which is usually carried out in conjunction with a more definitive surgical excision, will help differentiate tumor from other types of masses, such as infection. The microscopic structure of the tumor is vitally important in the pathologist's "grading" of the tumor.

Tumor Grade

Tumor grading is important for prognosis and therapy. Tumors are graded by microscopic examination of the tumor specimen. The specimen is evaluated for the most malignant components. Varying "grades" of tumor cells can be found in any one tumor. The biological behavior of the tumor will relate to the highest grade (worst and most aggressive) component of that tumor, even though that higher grade component comprises a small portion of the entire tumor. In other words, if a tumor is 99.5 % Grade 1 and only ˝ percent Grade 3 or 4, the biological behavior of that tumor, will be as if the entire tumor is Grade 3 or Grade 4.

Natural History

Astrocytomas are neither histologically or biologically uniform tumors. The borderline between low-grade (i.e. "non-aggressive) and Anaplastic (Malignant) Astrocytoma, can be quite indistinct. Although many patients with low-grade Astrocytomas survive for extended periods, 50% of surgically treated lesions evolve into Anaplastic Astrocytomas or Glioblastomas. Degeneration into a higher-grade neoplasm is the most common cause of death in patients with low-grade Astrocytomas.

Low-grade Astrocytomas

Low-grade Astrocytomas are uncommon tumors and occur less frequently than their more malignant counterparts. They are generally found in a younger population and have a more favorable prognosis. Their true incidence is difficult to determine, because sampling and grading vary substantially. Low-grade Astrocytoma probably represents 10% to 15% of Gliomas. These are neoplasms of children and adults from 20 to 40 years of age. These tumors are rare in older adults. Low-grade Astrocytomas can present with any of the symptoms previously described.

TREATMENT

Surgery

Surgery is important in order to remove the mass effect and pressure caused by the tumor. However, surgery is rarely curative for most infiltrating hemispheric Gliomas, unless the tumor is located at the anterior (front) portion of either a Temporal or Frontal Lobe.

Surgery is the principal treatment in the following situations of low-grade Astrocytomas:

  • Childhood Cystic Cerebellar Astrocytomas.
  • Supratentorial Pilocytic Astrocytomas.
  • Large tumors, or tumor cysts, causing severe pressure on the surrounding Brain.
  • Obstruction of Cerebrospinal Fluid (CSF) flow.
  • Seizure control for Epilepsy that is refractory to medical therapy.

Radiation Therapy

Radiation Therapy is the primary non-surgical treatment. Radiation can be administered to the whole Brain, or it can be relatively focused to a region of the Brain. Radiosurgery (Focused Beam Radiation) allows for very precise focusing of radiation beams into the area of Astrocytoma involvement, with less risk for damaging the surrounding Brain. Unfortunately, the energy from radiation is destructive to normal Brain cells, as well as, abnormal tumor cells.

In cases of incomplete removal of ordinary low-grade Astrocytomas, post-operative radiation is probably indicated.

When to Withhold Radiation Therapy

Consideration to WITHHOLD Radiation Therapy may be appropriate in cases of apparent gross total surgical removal, or incomplete removal, in cases of Pilocytic Astrocytoma or Cystic Cerebellar Astrocytoma. Meticulous follow up is required, since Radiation Therapy can be helpful where tumor recurrence or progression is documented.

Chemotherapy

Chemotherapy is usually not offered for patients with a low-grade Astrocytoma. Nevertheless, it may become appropriate if any progression of the tumor is subsequently noted.

Follow-up

LONG TERM FOLLOW-UP IS IMPERATIVE FOR THESE PATIENTS SINCE "RECURRENCE" AND PROGRESSION OF THIS TUMOR IS WELL KNOWN. EARLY RECOGNITION OF RECURRENCE CAN LEAD TO TIMELY INTERVENTION AND PROLONGATION OF AND HIGHER QUALITY LIFE.


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This page last edited on 2/19

All content ©2016 by Neurosurgical Consultants, P.A.
Author, Martin L. Lazar, MD, FACS
All Rights Reserved. See Usage Notices.