Which features of this tumour make a anaplastic astrocytoma more likely than a low grade glioma?
Both anaplastic astrocytomas and low grade astrocytomas appear similar on MRI, however the key to distinguishing them is the presence of enhancement which should be absent in the latter (although one should note that variants, especially gemistocytic astrocytomas, can demonstrate enhancement).
There is a lesion centered in the right temporal lobe which demonstrates extension into the posterior aspect of the frontal lobe in the precentral gyrus and the anterior aspect of the parietal lobe in the postcentral gyrus.
There is a small cystic appearing area within the anterior aspect of the lesion felt to represent a focus of necrosis.
There is a small amount of enhancement within the mid-portion portion and posterior aspects of the lesion. No evidence of hemorrhage or calcification appreciated. Moderate amount of surrounding vasogenic edema appreciated. Very minor mass effect on the adjacent lateral ventricle.
No midline shift. Ventricular size within normal limits and the basal cisterns are patent.
There are a few small foci of high signal within the white matter of the left hemisphere which are felt to be nonspecific. Incidental note of sinus disease. Vascular flow voids preserved.
Right temporal lobe tumor with involvement of the pre and postcentral gyri. Given the enhancement of the lesion, this is felt to most likely represent a grade 3 anaplastic astrocytoma.