Primary optic nerve sheath meningiomas arise from the arachnoid layer of the optic nerve sheath (Fig 15-14). They are less common than secondary orbital meningiomas, which extend into the orbit from a primary intracranial site, usually through the sphenoid bone. Although optic nerve glioma is a more frequent hallmark of NF1, meningioma may also occasionally be associated with neurofibromatosis in younger patients. Primary optic nerve sheath meningiomas may invade the nerve and eye and, in rare cases, may extend through the dura to invade the orbit and extraocular muscles.
Figure 15-14 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).
(Parts A and D courtesy of Nasreen A. Syed, MD.)
Histologically, the tumor (primary or secondary) is usually meningothelial, composed of plump cells with indistinct cytoplasmic margins (also called a syncytial growth pattern) arranged in whorls (see Fig 15-14D). Psammoma bodies, extracellular rounded calcifications surrounded by a cluster of meningioma cells, are variably present (see Fig 15-14D). Meningiomas are usually positive with the immunohistochemical stains epithelial membrane antigen (EMA) and somatostatin receptor 2a (SSTR-2). In addition, they also tend to express progesterone receptors.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.