The specimen being illustrated was removed from a 56 year-old woman. She has a history of invasive ductal carcinoma of the breast and was treated with surgery, chemotherapy, and radiation therapy. The tumor was located at the vertex of the brain adjacent to the midline. Which of the following is the most appropriate diagnosis?   Answer

A.  Meningioma with brain invasion

B.  Meningioma without invasion

C.  Astrocytoma with dural involvement

D.  Metastatic carcinoma to the brain with dural involvement

E.  Calcification and/or ossification of the dura

Answer and Discussion: The answer is (B). What is being shown here is a tumor with a smooth and symmetrical outline in the form of a nodule attached to the dura (dural based). This is most consistent with a meningioma without brain invasion. For cases with brain invasion, which is by definition of WHO grade II otherwise known as atypical meningioma, the brain tissue will be attached to the surface of the nodule. In this specimen, the surface of the nodule is smooth and clean and therefore no gross evidence of brain invasion.

Astrocytoma does not typically involve the dura. Due to their poorly demarcated nature, they cannot be separated from the brain with a clean plane of cleavage as in this specimen. Metastatic carcinoma can be attached to the dura and/or invades dura. However, they cannot be separated from the brain with a clean plane of cleavage as in this case. One must also note that metastatic carcinoma with involvement of the dura only can be seen. These tumors can mimic a meningioma both radiographically and on gross pathology. Metastatic prostatic carcinoma is a classic example. Also, metastatic carcinoma often, but not always, has necrosis. There is no necrosis in this case.

Calcifications or small bone resulted from ossification can be noted in the dura. Some of them may represented "burnt out" meningioma with calcifications and ossification. These lesions often are much smaller than the specimen being shown and the calcification would be obvious. There is no calcification or ossification of this specimen at least by looking at the external surface.