Brief overview
- Gradations: Among astrocytomas, there are benign and low-malignant (WHO grades 1 and 2) and malignant (WHO grade 3) to highly malignant forms (WHO grade 4). Benign forms often grow slowly or are well demarcated. Malignant variants usually grow rapidly and recur after treatment (recurrence).
- Treatment: Treatment options include surgery, radiation and/or chemotherapy.
- Causes: The triggers of the underlying genetic changes in glial cells are largely unknown. Presumably, there is a predisposition for the development of tumors, since, for example, hereditary diseases such as neurofibromatosis type 1 carry an increased risk. Likewise, strong radiation carries an increased risk.
- Diagnosis: In addition to physical examination, diagnosis is made with the help of ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), tissue examination (biopsy), and blood and hormone tests.
What is an astrocytoma?
What are the forms or gradations?
The World Health Organization (WHO) divides astrocytomas into two forms and four grades of severity:
1. benign to low-malignant (low-malignant) astrocytomas:
- WHO grade 1: Pilocystic astrocytoma
- WHO grade 2: Diffuse astrocytoma
Grade 2 High-malignant (malignant) astrocytomas:
- WHO grade 3: Anaplastic astrocytoma
- WHO grade 4: Glioblastoma
Pilocystic astrocytoma
This type of tumor is the most common brain tumor in children, but also occurs in young adults. It usually grows in the anterior visual pathway, hypothalamus or cerebellum. It separates well from healthy brain tissue and grows slowly. Thus, this type of tumor is considered benign – extremely rarely it progresses to a malignant tumor.
Diffuse astrocytoma
Diffuse astrocytoma is considered to have limited benign or low-grade malignancy, although it is almost never curable. It is possible for it to progress to the anaplastic type or glioblastoma over time.
Anaplastic astrocytoma
Glioblastoma
Glioblastoma, the most common type of astrocytoma, either arises from another astrocytoma – in which case the peak age of affected individuals is between the ages of 50 and 60. Or a primary “de novo” glioblastoma develops. This predominantly affects older people in their sixth to seventh decade of life.
For more information, see the article Glioblastoma.
Therapy of an astrocytoma
In the case of circumscribed tumors, brachytherapy is sometimes considered. For this purpose, the physician implants small radioactive grains (seeds) into the affected body region. The advantage of this form of radiation is that it hits the tumor very specifically and damages less healthy tissue.
In addition to these therapeutic measures, there are numerous other treatment measures that do not combat the tumor itself, but do combat the symptoms. For example, doctors administer various medications for headaches, nausea and vomiting. In addition, professional psychotherapy is usually part of the treatment plan. Some sufferers make use of pastoral care.
More detailed information on examination and treatment can be found in the article Brain tumor.
The course of the disease and prognosis depend essentially on the specific form of the astrocytoma.
In contrast, an astrocytoma with WHO grade 2 or 3 has a significantly worse prognosis. Second- and third-grade astrocytomas are usually operable, but often return (recurrences). In some cases, tumors of both forms degenerate malignantly and progress to glioblastoma (WHO grade 4). This has the worst prognosis: five years after diagnosis, only five percent of those affected are still alive.
What causes an astrocytoma?
An astrocytoma arises from so-called astrocytes. These cells make up the largest portion of the supporting cells (glial cells) in the central nervous system. They demarcate the nervous tissue from the brain surface and blood vessels. Just like other cells in the body, astrocytes are regularly renewed. In some cases, errors occur during this process that lead to uncontrolled cell growth and eventually to a tumor.
In addition, this form of brain tumor occurs more frequently in certain underlying diseases, which are usually inherited. These include neurofibromatosis type I (von Recklinghausen’s disease) and type II, tuberous sclerosis (Bournville-Pringle’s disease), Li-Fraumeni syndrome and Turcot syndrome. These diseases are very rare and are usually accompanied by typical changes in the skin.
What are typical signs?
Fast-growing tumors not only displace individual brain structures, but also increase intracranial pressure. As a result, those affected usually have headaches and suffer from nausea and vomiting. In principle, an astrocytoma causes similar symptoms to other brain tumors.
For more information on symptoms of a brain tumor, read the article Brain Tumor – Symptoms.
Diagnosis of an astrocytoma
The most important diagnostic procedure for astrocytoma is magnetic resonance imaging (MRI) – an imaging technique that uses magnetic fields and electromagnetic waves to produce precise cross-sectional images of the inside of the body. Affected individuals often receive a contrast agent injected into a vein before the examination. Astrocytomas absorb the contrast medium to varying degrees.
If MRI is not possible for various reasons, the physician uses computed tomography (CT) as an alternative.
In the case of an astrocytoma of WHO grade 2 or higher, the physician takes a tissue sample and examines it in the laboratory. In individual cases, further examinations are indicated. In some cases, for example, the physician additionally takes and analyzes cerebrospinal fluid (CSF diagnostics) or performs a measurement of the electrical brain waves (EEG).