Meningioma (dual component)
The patient went on to have a resection.
The sections show a moderately cellular meningioma with focal infiltration into the adjacent dura. The tumor forms sheets and whorls. The tumor cells have ovoid nuclei with mild nuclear pleomorphism and focal conspicuous nucleoli. The background is focally myxomatous with embedded cords of tumor, giving a chordoid-like appearance. This pattern is present in less than 50% of the tumor. There are up to 4 mitoses per 10 high power fields. No necrosis is found. No brain parenchyma is seen. No evidence of malignant change is identified. The features are those of atypical meningioma. The tumor cells are diffusely progesterone receptor positive. The Ki-67 index is about 8%.
DIAGNOSIS: Atypical meningioma (WHO Grade II) with bone invasion by tumor identified.
This case is a fantastic example of how just looking at a DWI isotropic image is not sufficient to estimate degree of restricted diffusion. In this example the anterior component is low on T2 and has significant restricted diffusion (~700 x 10-6 mm2/s) whereas the posterior component has high T2 signal and facilitated diffusion (1200-1500 x 10-6 mm2/s), and yet both components appear similar of DWI due to variable T2 shine through.