Optic nerve sheath meningioma. A, Gross photograph showing a globe (white bracket) with massive thickening (red bracket) of the optic nerve and sheath just posterior to the sclera, secondary to meningioma. B, This meningioma (asterisks; different from that shown in part A) has grown circumferentially around the optic nerve (outlined by dashed line), compressing and deforming it (arrowhead indicates the dura). C, Meningioma (between arrows) of the optic nerve sheath originates from the arachnoid layer of the meningeal sheath. D = dura; ON = optic nerve. D,High magnification of meningioma. Note the characteristic tumor whorl (arrows). A calcified psammoma body is present adjacent to the whorl (arrowhead).