This video is the third video in an overview about the emergent approach to brain tumor imaging. This video talks about different presentations of the most common primary brain tumor type, astrocytomas, ranging from grade 2 to grade 4, showing representative emergency presentations and CT examples with emphasis on how to report the CT and next steps.
Types of astrocytomas.
Astrocytomas range from grade 2 to grade 4, with the highest grade IDH wild type tumors being glioblastomas. Some lower grade gliomas behave like higher grade tumors if they have specific molecular features.
Case 1. Grade 2 Astrocytoma.
There is a low density mass in the insula and temporal lobe with moderately well-defined margins. The differential primarily includes tumor and infection with stroke and metastatic disease less likely. The MRI shows primarily a non-enhancing mass in the medial temporal lobe and insula with a lot of expansion.
Grade 2 astrocytomas tend to be younger patients and have IDH mutation. Common locations are the frontal and temporal lobe. Enhancement, hemorrhage, and cyst formation are relatively rare.
Case 2. Grade 3 Astroctyoma.
In this case, there is a more heterogenous mass in the right basal ganglia and corona radiata. Internal areas of high density may represent some areas of calcification or hemorrhage. There is definitely more mass effect. In your differential, you would think about an intermediate grade tumor or metastatic disease. The MRI confirms that there is a more heterogeneous mass with some faint/subtle areas of enhancement centrally. This makes you think of an intermediate to higher grade tumor.
Grade 3 astrocytomas, or anaplastic astrocytomas, make but about 25% of astrocytomas. They tend to be a little less defined and are more likely to have cysts, enhancement, and hemorrhage
Case 3. Grade 4 Astrocytoma
The CT in this case shows a much more heterogeneous mass spanning both frontal lobes and involving the corpus callosum. The high density material internally likely represents hemorrhage. There is a lot of mass effect on the frontal horns bilaterally. In this case, you are definitely thinking about a high grade mass or metastatic disease. Lymphoma would be less likely. The MRI confirms what you saw on the CT, with lots of internal hemorrhage, mass effect, and extension across the corpus callosum. There is a lot of heterogeneous and ill-defined enhancement.
Grade 4 astrocytomas are either glioblastomas (if they are IDH wild type) or IDH-mutated grade 4 astrocytomas. This was a case of glioblastoma. These tumors frequently have a hemorrhage, mass effect, and heterogeneous enhancement.
In this video, we’ve seen a range of astrocytomas and how they can appear on imaging, particularly on CT. Hopefully you learned a little bit about how to form a differential on CT and give an appropriate differential.
Be sure to tune in for upcoming videos which will cover oligodendrogliomas, other common tumors, and some red flags to be alert to in the ER setting.