Histopathology of meningiomas and gliomas of the optic nerve

H I S T O P A T H O L O G Y OF M E N I N G I O M A S A N D G L I O M A S OF THE OPTIC NERVE Merlin D. Marquardt, MD,* and Lorenz E. Zimmerman, M D t The origin, histologic features, and problems in the histopalhologie diagnosis of orbital meningiomas and gliomas are discussed. Special emphasis is given to distinguishing between arachnoidal hyperplasia and meningioma, identifying the origin of meningioma, and distinguishing between the following tumors: meningioma and fibrous histiocytoma or hemangiopericytoma; metastatic carcinoma and meningioma; piloeytic astrocytoma and neurilemoma; and reactive gliosis and astrocytoma. Hum Pathol 13:226-235, 1982.

The opti c nerve is a myelinated fiber tract of the central nervous system. Like the brain and spinal cord it is covered by meninges (fig. 1). The optic nerve consists mainly of the myelinated axons of the retinal ganglion cells and supporting oligodendroglia and astroglia. The glial elements of the nerve are tim apparent source of optic gliomas. In the orbit the optic nerve is divided into numerous fasciclesby pial septa that are internal extensions o f the relatively thick fibrous pia, which intimately invests the nerve (fig. 1). Delicate fibrous trabeculae traverse the subarachnoid space between the pia and arachnoid.~ The arachnoid is a tlfin fibrovascular tissue containing scattered clusters of meningothelial cells, sometimes referred to as aractmoidal cap cells (fig. 2). Meningothelial cells are present throughout the arachnoid of the entire central nervous system and are considered to be tile p r i n c i p a l cells o f origin o f m e n i n g i o m a s . T h e arachnoid is loosely a p p o s e d to the thick fibrous dura. In the orbit tile dura of the optic nerve merges anteriorly with the sclera of the eye, whereas posteriorly it is firmly united with the periosteum of the optic foramen. Two important neoplasms arise within the orbital p o r t i o n o f the optic n e r v e and its m e n i n g e s - meningiomas and gliomas. MENINGIOMAS Meningiomas arise from meningothelial cells normally present in the arachnoidal sheath of the Received from the Registry of Ophtlmlmic l'axhology, Armed Forces Institute of Patlmlogy (AFIP), Washington, DC 20306. T h e opinions aml assertions contained herein are tim private views o f the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. * This work was initiated while Dr. Marquardt was a Fellow in Opllthahnic Pathology, AFIP. Doctor Marquardt is currently Assistant Professor of Oplltlmlmic Pathology and Neuropathology, College of Physicians and Surgeons of Cohtmbia University, and Director, Algernon B, Reesc Laboratory of Opllthahnic Pathology, T h e Edward S. Harkness Eye Institute, Columbia-Presbyterian Medical Center, New York, NY. "~Chairnmn, Department of Ophthahnic PathologT, and Registrar, Registry of Ophthahnlc Pathology, AFIP. Address correspondence a n d reprint requests to Dr. Zimmerman.

226

optic nerve (figs. 1 and 2). Tile)" have histologic features very similar to those o f intracranial meningiomas. Meningiomas are conventionally classified into several histologic variants: meningotheliomatous, p s a m m o m a t o u s , fibroblastic, transitional, and angioblastic, ta T h e meningotheliomatous or "syncyliar' type (fig. 3) is composed of neoplastic meningothelial cells resembling the meningothelial cells normally present in the arachnoid. Cellular margins are indistinct in routine preparations, and the tissue appears to be a syncytium. Ultrastructurally, cytoplasmic extensions o f adjacent neoplastic cells are complexly interdigitated. The neoplastic cells are arranged ill lobules and often form characteristic whorls. Concentrically laminated concretions, psammorea bodies (fig. 4) may be present in various numbers. When they are especially numerous and conspicuous, tile designation psammomatous meningioma is often used, but such tumors are rarely encountered in the optic nerve (fig. 5). Lipid-laden xanthoma cells may also be present. The nuclei o f neoplastic meningothelial cells are usually oval and lightly stained, altltough occasionally they may be disturbingly pleomorphic and hyperchrontatic. An infrequently recognized feature is the presence of mucoproteinaceous intracytopIasmic inclusions? Fibroblastic meningiomas are composed o f elongated slender neoplastic meningothelial cells resembling fibroblasts. The cells are arranged in sheets and interwoven fascicles and are interspersed with various amounts o f collagen. T h e transitional type of meningioma contains areas with features of both meningothelial .and fibroblastic m e n i n g i o m a s (fig. 6). Angioblastic meningiomas resemble hemangiopericytomas or hemangioblastomas. Vascular and fibroblastic tumors encountered in the orbit are only rarely of meningeal derivation and shotfld not, therefore, be classified as meningiomas, unless they are clearly demonstrated to be intradural tumors. Virtually all primary intraorbital meningiomas are of the meningotheliomatous or transitional type. 4 It is important to realize that a primary intracranial meningioma may secondarily extend into the orbit, with or without involvement of tile optic nerve (fig. 7). The primary intracranial tumor in such cases may be clinically silent, and the orbital meningioma may be inappropriately designated an ectopic meningioma. Theoretically, however, a meningioma may arise in the orbit from ectopic meningeal tissue. Meningiomas may also be nmhicentric, especially in patients with yon Recklinghausen neurofibromatosis, who may lmve separate primary intracranial and in-

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HUMAN PATHOLOGY--VOLUME 13, NUMBER 3 March 1982 traorbital tulnors. Classified according 10 their sites o f origin, therefore, orbital nmningiomas may be: 1. I'rinmry tumors in optic nerve 2. Secondary invadersj from intracranial sites o f origin a. with optic nerve involvetnent b. without optic nerve involvement 3. Muhicentric tumors with separate sites o f origin intracranially and in optic nerve 4. Ectopic extradural tUlnOrs Froth a practical standpoint, almost all orbital meningiomas fall into groups 1 and 2b. When an extradural meningioma is encountered either in the orbit or in the periorbital facial region, it should be assumed to be the result o f spread front an intracranial primary site, even though p r o o f may not be imntediately demonstrable. Only by a meticulously t h o r o u g h postm o r t e m examination o f the orbit, optic nerve, and intracranial structures can one be relatively convinced that an extradural orbital meningioma is truly ectopic. Multicentric Ineningionms Inay also be exceedingly difficult to differentiate from metastasis along the meningeal surfaces from brain to optic nerve attd vice versa. Meningiomas arising in tim aracltnoid o f the optic nerve may at first remain intradural, occupying and e x p a n d i n g the subarachnold space and COlnp r e s s i n g the optic n e r v e (fig. 8). T h e r e m a y be ntarked papilledenm when the t u m o r lies close to the globe (figs. 5 and 9). Eventually, however, the meningionm will typically invade into and t h r o u g h the d u r a to form a large or diffuse extradural orbital ntass (figs. 9 and 10). Usnally the optic nerve is s u r r o u n d e d or displaced b)' the tumor, and the nerve degenerates and becomes atrophic. T h e pare,tchynm o f the optic nerve nmy also bc infiltrated by neoplastic nteningothelial cells. Rarely, the optic papilla, retina, or cltoroid may be involved. Orbital bones may be invaded, but this is more c o m m o n l y observed with intracrataial meningiontas that invade the orbit secondarily. Alt h o u g h m e n i n g i o m a s . a r e often highly invasive in orbital tissues, the)' rarely metastasize; in this respect tltey are considered benign neoplaslns. Because of their invasiveness, however, cotnplete excision is difficult, and the residual neoplastic tissue tends to continue to proliferate, resnlting in recurrence and possible fllrther extension of the tumor. A l t h o u g h meningiomas are observed more fi'equently in adults than in children, they are not as rare in children as was once thought. T h e i r aggressive behavior appears to

be greater and their prognosis worse a m o n g pediatric patients. 4.5 GLIOMAS

Optic gliomas (fig. 11) arise from tim glial cells (fig. 1) o f the optic nerve. Almost all optic gliolnas are very low-grade pilocytic astrocytomas; the histology o f these tumors (figs. 12 througll 15) is similar to that o f lbilocytic astrocytomas occurring in the cerebellum and in the region o f tile third ventricle? ,-0'6 When confined to tim orbital segment o f the optic nerve, these tumors carry a favorable prognosis c o m p a r e d with that of tnmors arising within the chiasln. ~ Some portions o f optic gliomas may have the appearance o f an oligodendroglioma. In ahnost all tlmse tumors, neoplastic astrocytic cells are also present and usually predominate. Most optic gliomas are histologically and clinically benign neoplasms, but there are rare inalignant optic gliomas, s-~~ T h e histopathologic criteria for malignancy of optic glionms include those features of nmlignancy of glionms elsewhere in the central nervous system, such as dense cellularity, high mitotic index, m a r k e d pleolnorphism, necrosis, and vascular proliferation (fig. 16). Gliomas arising within the region of the hypothalamus or in tim optic chiasm may infiltrate the hypothalamus or extend into the intraorbital portion o f the optic nerve. T h e following discussion pertains to p r i m a r y gllomas o f the intraorbital portion o f the optic nerve. Recently the general aspects of optic gliomas lmve been extensively reviewed. T M Pilocytlc astrocytomas o f the optic nerve are composed o f highly elongated neoplastic astrocytic cells with long fibrillary processes (figs. 12 and 13). T h e astrocytic processes may be stained blue with a p h o s p h o t u n g s t i c a c i d - h e m a toxylin stain. Some neoplastic cells may be stellate or multipolar rather than bipolar (fig. 14). Within the substance o f the nerve, neoplastic astrocytes lnay be exceedingly difficult to distinguish from reactive astrocytes, especially in the regions o f transition from neoplasm to nerve. Nuclei o f the neoplastic cells are slightly h y p e r c h r o m a t i c and mildly to m o d e r a t e l y pleomorphic. Cells in ntitosis are rarely seen. T h e neoplastic pilocytic astrocytes proliferate within the fascicles of the optic nerve and tend to align themseh'es with their long axes oriented along the axis o f the nerve (fig. 12). T h e neoplastic ceils also invade and thicken the pial septa. Snmll cystic spaces con-

Figure 5 (top left). Tile myriad black spots scattered throughout this meningionla are psammoma bodies. It is exceptional to find so many psamnmma bodies in meningiomas of the optic nerve. A striking degree of chronic papilledema is present. (x000. AFII' neg 70-5812.) Figure 6 (top right). Transitional meningioma of optic nerve. Ahhough some features are similar to those of meningotheliqmatous meningiomas, the cells tend to become more elongated, like those in the libroblastic type. (x115. AFIP neg 67-3074.) Figure 7 (bottom left). Massiveorbital invasion by meningioma ofintracranial origin. Although the optic nerve is surrounded bytumor, the tumor is entirely extradural. (x.t. AFIP neg 76-8010.) Figure 8 (bottom right). An extreme degree of intradural growth of meningioma with atrophy of the optic nerve. (x 13. AFIP neg 71-4679.)

228

OPTIC NERVE MENINGIOMAS--MARqtJARDT, ZIMMERMAN

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taining a mucoid material demonstrable with alcian blue may be a prominent feature. Larger accumulations o f this extracellular material may account for a clinically signiticant increase in proptosis. ~z T h e neoplasm in the nerve ma)' grow t h r o u g h t h e pia s u r r o u n d i n g t h e n e r v e a n d i n t o the arachnoid, where it clmracteristicall)' provokes an exuberant reactive proliferation o f fibroblastic tissues and meningothelial cells. Because the neoplastic astrocytes becotne intermixed with reactive fibroblasts, reticulin fibers, collagen, and meningothclial cclls, the h i s t o l o g i c a p p e a r a n c e o f tile t u m o r w i t h i n thc arachnoid is usually somewhat different from its appearance within the optic nerve, and the fascicttlar pattern is less evident. T u m o r cells may be st) intimatel)' intermixed with fibroblasts that the)' ma)' be very difficuh to recognize and identif)'. Fibrosis, with 230

F i g u r e 11. Pilocytic astrocytoma, which arose in the posterior orbital segment o f the optic nerve, Ires destro)'ed the architecture o f the nerve and massively invaded the aracbnoid, but the dura (arrows) remains intact. T h e t u m o r extends forward between the dura and the pial surface of the nerve toward the globe. (:<7. AFIP neg 81-16521.)

or without hyalinization in tlte subarachnoid space, ma)' become inarked a n d extensive. T h e araclmoidal thickening nmy extend well be)'ond the margins of tile neoplasm (figs. I 1 a n d 17). Thus, the characteristic enlargement o f an optic nerve involved b)" an optic glioma ma)' be due to a combination of (1) proliferation of neoplastic astrocytes in the fascicles and pial septa of the nerve, (2) an accumulation of extracellular material in cystic spaces within the neoplasm, a n d (3) a reactive proliferation o f araclmoidal tissue in response to arachnoidal invasion b)" the glioma. Whereas invasion o f the arachnoid is common, infiltration o f the d u r a and extradural extension are extremel)" rare. Even after incomplete resection o f an optic glioma, recurrence with invasion o f the orbital tissues is rarely observed.

OPTIC

Two strikingly different growth pattcrns are observcd among optic gliomas. One is clmracterized by a marked thickening of the parenchyma of the nerve with minimal growth of the tumor in the arachnoid and little or no reactive proliferation of araclmoidal tissues (fig. 18). In the second, such massive, diffuse thickening of the arachnoid occurs that much of thc enlargement of the optic nerve is attribntable to invasion o f the arachnoid and the consequent reactive proliferation of araclmoidal tissues (fig. 11). Recently it Ires been suggested tlmt this pattern of extranettral growth of glioma in the subarachnoid space is especially characteristic of optic gliomas in patients with n e u r o f i b r o m a t o s i s and that in patients wititout neurofibromatosis, the glioma tends to remain confined to the paranchyma of the optic nerve? ~

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In some cases the hyperplasia of arachnoidal meningothelial cells may be so exuberant that it simulates the appearance of a meningioma, ~4not onl)' in small biopsy specimens but also when an entire tumor is available for histopathologic study as, for example, in the case o f a tumor interpreted as a mixed meningioma and astrocytoma by Shuangshoti and PanyathanyaY ~s Clusters of meningothelial cells in small biopsy specimens may be very difficult to interpret, since it may be impossible to determine whether these clusters o f meningothelial cells represent meningioma or meningothelial hyperplasia in the absence of identifiable neoplastic astrocytes. Clusters of meningothelial cells within the dura or in an e x t r a d u r a l location are highly suggestive of meningioma, but the pathologist must exercise cau-

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(top left). This pilocytlc astrocytoma (A) has produced increased.cellularity and irregular tlfickening of compartments

normally occupied mainly by optic nerve fibers, and t h e r e is thickening o f tile plal septa (S). (x55. A F I P ncg 65-4152.) Figure 13 qop right). Interlacing fascicles o f s l e n d e r elongated pilocytic astrocytes. (x80. A F I P neg 67-3111.) Figure 14 (bottom left). M u c h m u s d e g e n e r a t i o n in pilocyfic astrocytoma. T h e t u m o r cells have m o r e a b u q d a n t cytoplasm and irregular, sometimcs stellate processes. (x400. AFIP neg 61-651.) Figure 15 (bottom right). Densely stained, thick hyalinized astrocytic cell processes (Roseqthal fibers), which are frequently observed in pilocytic astrocytomas o f the optic nerve. (x600. AFIP neg 61-650.)

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HUMAN PATHOLOGY--VOLUME

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Figure 16. Malignant glioma of optic nerve. Top left, extensive necrosis centrally, and marked vascularity peripherally. (• AFIP neg 76-7739.) Top right, cellular pleomorphism with many neoplastic giant cells, and vascular proliferation. (• 115. AFIP neg 76-7738.) Bottom right, palisading of pleomorphic tumor cells about area of necrosis and a focus of neovascularization. (• AFIP neg 76-7742.)

232

March 1982

OPTIC NERVE MENINGIOMAS~MArQUARDt, ZIMXterMAN

Figure 17. Extrememeningeal thickening due mainly to reactive arachnoidal hyperplasia and fibrosis remote from the glioma. This field corresponds to the area in figure 11 jtlst posterior to the globe on the top side of the optic nerve. (x32. AFIP neg 81-16522.)

tion in the interpretation o f small biopsy specimens, because hyperplastic meningothelial cells e m b e d d e d in dense fibrous tissue may be mistaken for cells invading the dura. R o s e n t h a l fibers a r e f r e q u e n t l y p r e s e n t in pilocytic astrocytomas. Rosenthal fibers are irregular cylindrical, spherical, or conical structures (fig. 15) associated with neoplastic or reactive glial tissue. The)' have a hyaline eosinophilic appearance when stained with hematoxylin anti eosin and are bright red with the Masson stain, light blue with a Luxol fast-blue stain, and dark blue to purple with a phosphotungstic acid-hematoxylin stain. Ultrastructurally, Rosenthal fibers are composed of electron-dense granular material and associated glial filaments (microfilaments). z In older, often m a r k e d l y fibrotic lesions that contain no recognizable neoplastic cells, the presence o f Rosenthal fibers is very strong presumptive evidence o f an optic glioma, especially when located within an arachnoidal mass where reactive astroc),tes would not be expected. Older fibrotic gliomas tnay contain n u m e r o u s blood vessels with thick fibrotic walls, a n d the a p p e a r a n c e m a y be m i s l e a d i n g l y suggestive o f an a n g i o m a t o u s lesion. A histocytic reaction may be associated, the histocytes containing an a b u n d a n c e of lipid or blood pigments or both. Optic gliomas with these degenerative features may be designated "ancient" gliomas, in analogy to "ancient" schwannomas that exhibit similar degenerative features. In less advanced optic gliomas there may be remarkable sparing o f nerve fibers in regions of the optic nerve that are diffusely infiltrated a n d thickened by neoplastic astrocytes. Axons tend to persist longer than myelin sheaths. T h e sparing o f these n e u r a l elements may be readily d e m o n s t r a t e d by means o f appropriate special stains.

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233

HUMAN PATIIOLOGY--VOLUME 13, NUMBER 3

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PROBLEMS IN HISTOPATHOLOGIC DIAGNOSIS

ht dealing with orbital tuntors, it is very important for the surgical pathologist to have as must clinical inforlnation as possible before r e n d e r i n g a diagnosis. Tim pathologist must also k n o w prccisely where in the orbit the t u m o r was located, and, in the case o f optic nerve lesions, whetiter the biops)' specimen was obtained from an e x t r a d u r a l mass or f r o m intradural tissue. C o m p u t e d t o m o g r a p h y has p r o v e d v e r y h e l p f u l in p e r m i t t i n g t h e s u r g e o n to a s c e r t a i n preoperatively w h e t h e r an orbital t u m o r is intraconal o r extraconal and, if intraconal, whetlter it is intradttral o r extradural. T h e surgical pathologist should also have tim benefit o f this information. 1. ARACtlNOII)AL HYI)ERI'LASIA OR ~I'ENINGIo,xm. I'seudomeniiIgiomatons proliferation o f ineifingothelial cells is a well-known p h e n o m e n o n observed in association with some pilocytic astrocytomas o f tim optic nerve, yet it continues to present practical problexns for the surgical pathologist, especially when only small biopsy specimens are available for s t u d y ) 4 In chiklren, gliomas o c c u r far m o r e frequently than do meningiomas a m o n g t u m o r s o f the optic nerve, and for this reason alone the pathologist shoukl be very reluctant to r e n d e r a diagnosis o f meningioma unless the evidence is qttite convincing, tlowevcr, the patimlt)gist c a n n o t a f f o r d to ignore complacently the possibility o f a ntcningioma, regardless o f the patient's a g e : Meningiotnas o f the optic nerve are not as rare in childreI~ as some authorities state, and they carry a m u c h worse prognosis than do pilocytic astrocytomas, a T h e tncningothelial hyperplasia that one sccs with gliomas is typically focal and m u c h less conspicuous than the accontp,utying fibroblastic and histiocytic reaction that astrocytic invasion o f tile arachnoid st) frequently provokes. It also remains intradural. Unequivocal d e m o n s t r a t i o n o f nests o f meningothelial cells infiltrating the d u r a or inwtding extradttrally into adipose tissne o r extraocular tnuscle indicates a meifingiotna. In reactive Ineningothelial hypcrplasia, the cells tend to be smaller and to have less conspicuous nttclei than in g e n u i n e meningiomas. 2. ORIGIN OF A ~IENINGIOMA. With small biopsy speciniens the pathologist can rarely be e x p e c t e d to deterntine the origin o f a meningioma. In the absence o f visual loss or evidence o f an e n l a r g e d optic nerve, it is most likely that an orbital ntetfingionta arose intracranially and invaded tllat orbit secondarily. It is not exceptional fox" the intracranial site o f origin to be asyntptonlatic and for an orbital o r facial mass to be the p r e s e n t i n g ntanifestatiola. 3. ~IENINGIOMA VS. FIBROUS IhsTIOCYTOMA OR HEMANGIOI'ERICVTOMA. F i b r o u s h i s t i o c y t o n t a s , helnangiopericytonms, and t u m o r s exhibiting mixed features o f these arise in the orbit r a t h e r m o r e frequentl)' than in most o t h e r tissues. Whell such t u m o r s are e n c o t m t e r e d intracranially, neuropathologists will generall)" classify them as fibroblastic o r angioblastic meningiotuas. T h o s e that arise in the orbit, however,

234

rarely if ever are related either to a ntass in the optic nerve or to an intracranial tumor. It would, t h e r e l b r e , be clearly i n a p p r o p r i a t e to label these orbital tumors meningiomas. 9t. ~ I E I ' A S T A ' i ' I C CARCINOMA OR ~[ENINGIOMA. T h e lfistologic a p p e a r a n c e o f some meningothclial mcningiomas may suggest a squamous cell carcinoma, and the meningothelial whorls may be mistaken for epithelial pearls o f a keratinizing e p i d e r m o i d carcinoma. In o t h e r instances the gland-like formations and intracytoplasmic m u c o p r o t c i n a c e o u s vacuoles may be misilaterpreted as evidence o f a d e n o carcinotna. We recently saw such a case in consuhation, in which a ntass in the temporal muscle and orbit was mistaken for an adenocarcinoma. Clinically and radiologically it may also be impossible to distinguish between a s q u a m o u s cell carcinoxna o f tile paranasal sinuses that invadcd the orbit and cranium and an intracranial n l e n i n g i o m a that i n v a d e d the paranasal sinuses and orbit. 5. PILOCYTIC ASTRt)CY'I'OMA OR NEURILEMt)MA. T h e s e tumors can have virtttally identical hlstologic appearances; when they do, it is very helpful for the pathologist to know tile location o f the tttntor within tim orbit and its r e l a t i o n s h i p to the optic nerve. R e m e m b e r that the optic nerve is part o f tim central ner,;'ous system and that neurilcmomas arise from the peripheral nervous s)'stem. A t u n t o r tliat is not intradural c a n n o t be an astrocytonta o f tire optic nerve. Sometimes it is difficult to differentiate b e t w e e n the d u r a a n d the f i b r o u s c a p s u l e o f a n e u r i l e i n o l n a , b u t g e n e r a l l y tile c a p s u l e o f a neuriletnonta is t h i n n e r and more intimately adher= ent to the ttmtor than is the dura. If at-achnoidal tissue o r Rosenthal f b e r s can be identified, tlIe t u m o r a r i s e s f r o m tlm o p t i c n e r v e a n d c a n n o t be a neui'ilemoma. Staining lbr argyroplti]ic reticulin fibers may be helpful, since the n e u r i l e n m m a in some areas sliould show the characteristic fibers paralleling tlm It)rig axis o f the t u m o r cells. Electron microscop)' o f n e u r i l e m o m a s reveals collagen antl b a s e m e n t m e m b r a n e ntaterial s u r r o u n d i n g t u m o r cells, featttres that are not cltaracteristic o f gliotnas. 6. REACTIVE GIAOSIS OR ASTROCYTOMA. In optic neuritis the d e g r e e o f gliosis may raise the question o f glioma. Fortunately, pilocytic astrocytomas are seldom complicated by any significant inflantmatory reaction. Thus, the presence of granulomas, a lynlphoplasmacytic infihrate, o r a p o l y m o r p h o n u clear reaction with or witllottt eosinophils should be taken as evidence that the glial proliferation is reactive. In s u c h cases t h e r e is g e n e r a l l y g r e a t e r pleomorphisnt titan in pilocytic astrocytonms. REFERENCES

I. Rubinstein LJ: Tumors of the central nervous s)'stem. Atlas of Tumor Pathology, Fascicle 6. Washington. DC, Armed Forces Institute of Pathology. 1972. 2. Burger I'C. Vogel FS: Surgical I'athology of the Nervous System and Its Coverings. New York,John Wiley& Sons, 1976. 3. Font RL, CroxattoJO: lntracellular inch+slonsin mcningothelial meiHngiuma.J Ncuropathol Exp Neurol 39:575, 1980.

O P T I C N E R V E MENINGIOMAS--MARQU,~RDT, ZIMMERb,IAN 9t. Karp LA, Zimmerman LE, Borit A, et al: l'rimary intraorbital meningiomas. Arch Ophthalmol 91:24, 1974. 5. Zimmerman LE: Araclmoid hyperplasia in optic nerve glioma. Br J Opthahnol 6't:638, 1980. 6. Russell DS, Rubinstein LJ: Pathology of Tumors of the Norwins S) stem. Bahimore, The Williams and Wilkins Co, 1977. 7. Yanoff M, Davis RL, Zimmerman LE: Juvenile pilocytic astroc)'toma "glioma" of optic ncrve: clinicopathology stud)' of sixty-thrce cases. In Jakobiec FA (ed): Ocular and Adnexal Tumors. Birmingham, Ala: Aesculapius Publishing Co, 1978, p 685. 8. llo)'t WF, Meshel LG, Lessell S, et ah Malignant optic glioma of aduhhood. Brain 96:121, 1973. 9. Hamilton AM, Garner A, Tripathi RC, et ah Malignant optic glioma. Report of a case with electron inicroscopic stud)'. Br J Ophthahnol 57:253, 1973.

10. Gibberd FB, Miller TN, Morgan AI): Glioblastoma of the optic chiasm. Br J Ophthalmol 57:788, 1973. 11. Eggcrs H, Jakobiec FA, Jones IS: Tumors of the optic nerve. Doc Ophthahnol 41:43, 1976. 12. Anderson DR, Spencer WI 1: Uhrastructural and histochemical observations of optic nerve gliomas. Arch Ophthahnol 83:325, 1970. 13. SternJ,Jakobicc FA, Houscpian EM: The architecture ofoptic nerve glionm with and without neurofibromatosis. Arch Ophthalmol 98:505, 1980. 1,t. Cooling RJ, Wright JE: Arachtmid hypcrplasia in optic nerve glioma: confilsion with orbital meningioma. BrJ OpHmlmol 63:596, 1979. 15. Shuangshoti S, Panyathanya R: Neoplasm of mixed mesenchymal and neuroepithelial origin of the optic nerve. Br J Opthahnol 61:390, 1977.

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