<unk>  in the hypothalamic region. Axial non-contrast CT in a nine-year-old girl showing a slightly hypodense mass in the tectum of the brainstem, compressing the aqueduct of Sylvius and causing obstructive hydrocephalus Sagittal T1-weighted MRI showing a well-circumscribed hypointense mass in the tectum (presumably a tectal plate glioma). These lesions are a distinct subset of<unk>  which present with hydrocephalus typically in 6 to 10 year-olds and are rarely progressive lesions. When imaging is characteristic, a biopsy is usually not performed because of the risks to adjacent structures, often shunting to relieve intracranial pressure is the only treatment required. T1-weighted coronal MRI image postcontrast showing heterogeneous contrast enhancement within the presumed tectal plate glioma Usually – depending on the interview of the<unk> tient and after a clinical exam which includes a neurological exam and an ophthalmological exam – a CT scan and/or an MRI scan will be performed to confirm the presence of a tumor. They are usually easily distinguishable from normal brain structures using these imaging techniques. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify.<unk> s are typically clearly visible on such scans, but it is often difficult to say based on imaging alone what type of tumor is present. If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy of it. This involves the removal of a small amount of tumorous tissue, which is then sent to a (neuro)pathologist for examination and staging. The biopsy may take place before surgical removal of the tumor, or the sample may be taken during surgery to remove the bulk of the tumor. Microscopic appearance<unk> s are often cystic tumors, and, if solid, tend to be well-circumscribed. Under the microscope, the tumor is seen to be composed of bipolar cells with long "hair-like" GFAP-positive processes, giving the designation<unk> " (that is, made up of cells that look like fibers when viewed under a microscope). Some<unk> s may be more fibrillary and dense in composition. The presence of Rosenthal fibers, eosinophilic granular bodies, and microcysts can often be seen. Myxoid foci and oligodendroglioma-like cells may also be present, though these are not specific to<unk> . Long-standing lesions may show hemosiderin-laden macrophages and calcifications.
Pilocytic astrocytoma
Fibrillary astrocytoma
Neurothekeoma
Pinealoma
Subependymal giant cell astrocytoma
Central neurocytoma
Subependymoma
Anaplastic astrocytoma