Gliomas are defined as tumours that tend to affect the glial cells within the brain. There are three main types of tumours that fit into this category: astrocytomas, oligodendrogliomas and ependymomas. In this page, I’ll be taking a closer look at astrocytomas.
What are astrocytomas?
Astrocytomas can come in several different categories, but the most well-known are fibrillary astrocytomas and pliocytic astrocytomas.
Fibrillary astrocytomas appear far more frequently than the pliocytic variety: fibrillary astrocytomas account for more than three quarters of the tumours of brain tissue which are diagnosed, and they tend to occur in people from forty to sixty years of age. They usually develop within the cerebrum, however they can occasionally affect the cerebellum as well. Fibrillary astrocytomas are named based on their appearance under the microscope; there are three separate grades, and they include the following:
- Anaplastic astrocytoma
- Glioblastoma multiforme
Astrocytomas are low grade, and glioblastoma mulitforme is the highest grade.
What do astrocytomas look like?
If you were to examine astrocytomas with the naked eye or encountered one within a pathology lab, you would see a grayish tumour with an edge that is hard to define. However, if you were to cut it open, it may appear quite different: the appearance of the tumour can vary depending on the grade of the tumour that you are looking it. The difference is quite apparent when you look at a tumour under an MRI scanner. In low grade astrocytomas, there are only subtle changes within the structure of the brain: the white matter would be expanded and the corpus callosum would be thickened.
How does glioblastoma multiforme appear?
However, in glioblastoma multiforme, the changes are obvious if seen under an MRI scanner: this happens because the blood vessels become abnormal, and due to these abnormalities, they have a tendency to leak. Additionally, if you were to see them when they are extracted, as the picture above shows, they are multi-coloured: some areas are white and firm other areas are yellowish. Glioblastoma multiforme appear similar to anaplastic astrocytomas, but they have also have necrotic tissue present. Unlike the other tumours, which are related to one another in the fact that the anaplastic version of astrocytomas are evolved from the lower grade astrocytomas, glioblastomas tend to get diagnosed straight away.
What do they feel like when you touch them?
If you were to touch astrocytomas, you might feel that some of the areas were jelly-like in consistency, but other areas are relatively firm: this tends to happen more frequently in tumours that are higher grade i.e. anaplastic and therefore more malignant in nature. To discover the relationship between differentiation and anaplasia and explanations for what they mean, see Benign Tumours vs. Malignant Cancers.
Compared to fibrillary astrocytomas, pilocytic astrocytomas tend to be relatively benign in nature; hence they are considered as low-grade tumours, and they are more often diagnosed in kids and in teenagers. Unlike fibrillary astrocytomas, pilocytic astrocytomas tend to affect several areas of the brain: usually within the cerebellum, but they can also hit the third ventricle, the cerebral hemispheres and the optic nerves. Under the microscope, these tumours are less solid in nature and appear more like cysts, and they do not have necrotic tissue. Additionally, there are hair-like projections that are bipolar cells.
What is the prognosis if you are diagnosed with one of these tumours?
The general rule with tumours is that the higher the grade, the poorer the prognosis. This is true in the case of brain tumours; however that is not the only factor that determines the prognosis due to the way the brain is structured. Another major factor that determines both the prognosis and the success of treatment is the location of the tumour within the brain. The deeper the tumour is located within the cerebrum, the poorer the prognosis. Astrocytomas that are well-differentiated tend to have a good prognosis, however the symptoms associated with tumours at this stage are fairly static or slowly progressing and may therefore be ignored or misinterpreted as related to other conditions. Patients with glioblastoma multiformae, unfortunately, have a poor prognosis: the majority of patients diagnosed with this tumour tend to not live after two years and the median survival rate is from 8-10 months, despite the best forms of treatment.
What are the symptoms of fibrillary astrocytomas?
Symptoms associated with fibrillary astrocytomas include the following:
- neurological defects which happen as a result of the tumour being within a certain area within the brain. Examples include blindness and deafness.