Various examples of meningiomas from a number of patients.
1. Gross specimen of a meningioma showing a tan, lobulated tumor with a broad-based dural attachment. Depending upon the predominant histologic subtype, the tumor may show cystic areas, whorled cut surface, gelatinous consistency, or areas of calcification.
2. The image shows "meningothelial" or "syncytial" meningioma - the most common histologic subtype. It is a WHO Grade I tumor. It is composed of monotonous appearing spindle cells arranged in short fascicles, syncytial structures, and whorls.
3. Atypical meningiomas are WHO Grade II tumors. They show increased mitotic activity (greater than or equal to 4 mitotic figures / 10 high power fields) AND one of the following features - hypercellularity, necrosis (shown here in the center of the image), prominent nucleoli, sheeting architecture, and small cells.
4. Anaplastic Meningioma, also known as Malignant Meningioma, is a WHO Grade III tumor. It presents with either of the following two criteria: 1) greater than or equal to 20 mitotic figures / 10 high power fields; 2) frank anaplasia with highly pleomorphic cells (showin in this image).