ABSTRACT
Most metastases differ from diffuse gliomas in that they form discrete, well-circumscribed spherical masses. The center of large metastases is often necrotic. The tumors may be cystic or hemorrhagic and occasionally even calcify. Intraparenchymal brain metastases usually arise just below the cortex at the gray matter-white matter junction and expand by pushing normal brain aside rather than invading it. A pseudocapsule can be identified in some tumors. Leptomeningeal tumors may appear only as thickening or as a decrease in translucency of the arachnoid membrane. Dural tumors may form dural plaques or nodules.
