Glioma tumours arise from a group of brain cells called glial cells. There are 3 types of glial cell, and if a tumour is mainly made of one of the three glial cells, the patient may be diagnosed with an astrocytoma, oligodendroglioma or ependymoma. However, sometimes it is not easy to tell.
The term 'unspecified glioma' is one which actually does not describe a single type of tumour. Also known as 'mixed glioma', this type of diagnosis was given in cases where either the doctors could not get a biopsy (sample of the tumour) to test or the biopsy was inconclusive, showing more than one type of glial cell being involved.
In its new classification for brain tumours in 2015 the World Health Organization (WHO) did not include unspecified glioma in the list of tumour types because the term doesn't really describe a single distinct type of tumour. The closest thing to an unspecified glioma in the new WHO classification is the oligoastrocytoma which describes a tumour that has both characteristics of an oligodendroglioma (from oligodendrocytes) and astrocytoma (from astrocytes).
Above: Illustration of the three types of glial cells surrounding a neuron. Biopsies of unspecified gliomas often show the involvement of more than one type of glial cell.
The World Health Organization discourages the diagnosis of tumours as unspecified glioma, mixed glioma or even oligoastrocytoma because they are too vague and unhelpful in finding the right treatment. There are a number of genetic marker tests (to test for IDH mutation and 1p/19q codeletion) which could determine whether a tumour is more like an astrocytoma or oligodendroglioma. Once the tests are done, your MDT will either treat the tumour as they would an oligodendroglioma or astrocytoma.
If you are diagnosed with an unspecified glioma, your team of specialists will treat your tumour according to what other type of brain tumour it most resembles to on scans and what type of cells are involved if it is possible to know. For example, if the tumour seems to be diffuse, which means it stretches into surrounding healthy tissue in a tentacle-type way, your team may want to treat the tumour with the maximum doses of chemotherapy and/or radiotherapy. If the tumour has well defined borders and seems not to be showing signs of growth, your team may choose to take a less aggressive treatment approach.
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