Glioma – A Patient Guide
Malignant gliomas of the cerebral hemispheres in adults are the most common primary brain tumors, and are thus the focus of our laboratory efforts. Malignant gliomas are classified as astrocytomas, oligodendrogliomas, and oligoastrocytomas. Surgical sampling allows for further WHO grading of these tumors, from Grade I (least-aggressive) to Grade IV (most aggressive). The most aggressive, Grade IV astrocytoma, is referred to as glioblastoma. Elucidating the molecular basis of glioma formation is impacting both diagnostic and therapeutic aspects of clinical neuro-oncology.
At MGH, we offer the full spectrum of modern care as well as promising new experimental therapies. We perform the highest volume of glioma procedures in New England, and are leaders in oncologic management of glioblastomas, and gliomas, and other less-common brain tumor subtypes. We are also home to the Cranial Base Program, which focuses on treating tumors of the cranial base, the junction between the brain and the face and neck.
Astrocytomas, oligodendrogliomas, and oligoastrocytomas are the most common primary tumors of the adult brain. These tumors are referred to as diffuse gliomas. Primary brain tumors arise from cells of the brain itself rather than traveling, or metastasizing, to the brain from another location in the body. Gliomas can be slowly growing (low-grade, grades I and II), or rapidly growing (high-grade, grades III and IV). This information has historically proven important for the diagnosis and treatment of gliomas.
High-grade gliomas are diagnosed by a biopsy, or an open resection of the lesion.
Once a brain tumor is detected on a CT or MRI scan, a neurosurgeon obtains tumor tissue for examination by a neuropathologist. The neuropathologist then assigns the tumor a name and grade. The exact name and grade of the tumor determine treatment options, and also give important information about prognosis.
When neuropathologists analyze tumor tissue under a microscope, there are two main questions being asked:
- What type of brain cell did the tumor arise from? The answer to this question gives the tumor a name, for example, astrocytoma.
- Do the tumor cells show signs of rapid growth? This involves assigning the tumor a grade, such as grade III or IV.
These two pieces of information are then combined, as in “grade IV astrocytoma”. Once a tumor has been given a name and a grade, brain tumor specialists can give advice about treatment choices, prognosis, and provide useful health-care information to brain tumor patients and their families.