Elmar P. Messmer

Immunohistochemical Demonstration of Neuronal and Astrocytic Differentiation in Retinoblastoma

Sections of 51 surgically enucleated eyes from cases of retinoblastomas were examined immunohistochemically to delineate patterns of cellular differentiation. Employing the avidin-biotin immunoperoxidase technique, antibodies were used against glial fibrillary acidic protein (GFAP), S-100 protein and neuron specific enolase (NSE). Areas of uninvolved retina and/or optic nerve were used as built-in positive control. Most of the tumors showed GFAP and S-100 protein-positive perivascular glial cells that were interpreted as reactive astrocytes. In three well-differentiated retinoblastomas, glial cells were found to be interspersed randomly among tumor cells and not associated with blood vessels. These glial cells were interpreted as neoplastic based on their distribution pattern and cytologic features. In about half of the tumors, the retinoblastoma cells stained positively for NSE, indicating their neuronal tumor cells that stained positively for NSE but failed to show any evidence of photoreceptor differentiation. Based on these observations and similar differentiation patterns described in other primitive neuroectodermal tumors of the brain, it is suggested that retinoblastoma cells can differentiate not only into photoreceptor cells but also along other neuronal cell lines and rarely into glial cells.

Hemangiopericytoma of the meninges of the optic nerve. A clinicopathologic report including electron microscopic observations.

A 61-year-old man complained of visual loss of his right eye following a systemic viral illness. At this time, complete ophthalmologic examination failed to disclose any abnormalities. Over the next months the patient developed dramatic loss of vision. Extensive workup, including CT scans, failed to clarify the underlying cause and a diagnosis of optic atropy following optic neuritis was made. The patient remained asymptomatic, but repeated CT scans depicted a fusiform enlargement of the intraorbital portion of the right optic nerve, three years after the onset of visual loss. The presumptive clinical diagnosis was optic nerve meningioma and the tumor was removed via a Krönlein procedure. Histopathologically, a highly vascularized intradural mass that led to compression atrophy of the optic nerve was present. The tumor was composed of fascicles of spindle-shaped cells that were interspersed among numerous, irregular vascular channels. Electron microscopically, the cells disclosed a lucent cytoplasm with a scarcity of organelles, prominent cytoplasmic filaments, numerous micropinocytotic vesicles and subplasmalemmal linear densities (hemidesmosomes). Poorly developed intercellular junctions were present between interdigitating cytoplasmic processes. The tumor cells surrounding the vascular units displayed a continuous basement membrane as well as all the features of well-differentiated pericytes. Away from vascular structures some tumor cells, which showed a focally discontinuous basement membrane, exhibited intermediate features between pericytes and fibroblasts. To the best of our knowledge, this is the first report of a hemangiopericytoma arising from the meninges of the optic nerve.

Light and Electron Microscopic Study of Dalén-Fuchs Nodules in Sympathetic Ophthalmia

A light and electron microscopic study was undertaken in an effort to establish the origin of the epithelioid cells in Dalén-Fuchs nodules from an eye enucleated because of sympathetic ophthalmia. The nodules were visible as minute (130-160 microns), round, grayish-white mounds elevating the retinal pigment epithelium. Bruchs membrane appeared intact in all the sections examined. By electron microscopy the epithelioid cells had round to oval nuclei with abundant, relatively lucent cytoplasm containing parallel profiles of rough-surfaced endoplasmic reticulum, prominent Golgi lamellae, clusters of polyribosomes, and scattered mitochondria. Many interdigitations of the plasma membranes, some of which exhibited fascia adherens type attachments, were observed. Some cells within the nodules showed large membrane-bound phagosomes containing laminated structures. Other epithelioid cells displayed moderately electron dense membrane-bound granules that appeared to be early precursors of lipofuscin granules. Examination of the nodules under ultraviolet light showed myriad autofluorescent yellowish-orange dots consistent with lipofuscin. Additionally, a montage of electron micrographs from the edge of the nodule, coupled with the above findings, provided support to the concept proposed by Ishikawa and Ikui (1972) that the epithelioid cells in Dalén-Fuchs nodules represent transformed retinal pigment epithelial cells forming a cage-like framework within the nodule. This study also emphasizes the remarkable capabilities for differentiation by the retinal pigment epithelial cells.

Amputation Neuroma of the Orbit: Report of Two Cases and Review of the Literature

Two patients developed proptosis and a slowly enlarging mass with increasing discomfort in the orbital socket 17 and 25 years following enucleation. Preoperative CT scans revealed a single cystic structure within the orbits of each case with distinct soft tissue tumors adjacent to the cysts. The cystic structures and the adjacent solid masses were removed en bloc necessitating reconstruction of the orbits with a dermal fat pad (case 1) and a mucous membrane graft (case 2). Postoperatively the patients were free of complaints. Microscopically, the cystic structures were identified as conjunctival inclusion cysts while the soft tissue masses were traumatic neuromas with irregular tangles and whorls composed of proliferated axons, Schwann cells and connective tissue. Only seven amputation neuromas of the orbit have been reported. Pain related to the neuroma is rarely encountered and is probably caused by mechanical irritation of the amputation neuroma, by retracting scar tissue, or compression from an adjacent cystic mass as in one of our cases.

Epithelioid Angiosarcoma of the Orbit Presenting as Tolosa-Hunt Syndrome: A Clinicopathologic Case Report with Review of the Literature

The clinical diagnosis of Tolosa-Hunt syndrome was first considered in a 66-year-old man with facial pain and diplopia. A complete neuroradiologic evaluation as well as an oncologic work-up yielded normal results. Several courses of oral prednisone provided no significant benefit. Within a year the patient became clinically worse and a CT scan disclosed an abnormal area of enhancement at the left orbital apex. An orbital exploration was performed elsewhere and a histologic diagnosis of myositis was obtained. Because of further worsening the patient was re-evaluated 3 months later and a CT scan showed a mass in the left orbital apex and superior orbital fissure. A second orbital exploration was performed and a sausage-shaped mass encompassing the optic nerve was excised. By light microscopy a poorly differentiated malignant tumor was infiltrating the orbital tissues with areas of intra- and perineural invasion. The tumor cells were arranged in strands and tubules with a definite tendency to form lumens that often contained red blood cells. Electron microscopic studies disclosed features consistent with a neoplasm of endothelial cell origin displaying a polarized basal lamina and rare micropinocytotic vesicles on the luminal side. The presence of multiple, slender microvilli and sometimes tonofilaments as well as desmosomes were interpreted as epithelioid metaplasia of an angiosarcoma.

Corneal Blood Staining: An Animal Model+

Corneal blood staining was established in the rabbit cornea by injecting autologous, citrate-buffered blood in the anterior chamber. Increased intraocular pressure was maintained above 30 mm of Hg by self-sealing trans-limbal injections repeated every 12 hours. Typically, corneal edema developed in 3 days, followed several days later by a red discoloration that turned brown about 2 days later. Histopathologically, the edematous cornea disclosed endothelial swelling and attenuation with marked stromal edema. Histochemically, the red-stained cornea disclosed only extracellular hemoglobin particles; the brown-stained corneas showed extracellular and intracellular hemoglobin particles as well as intracellular hemosiderin in keratocytes. Spectrophotometric analysis of the keratectomy specimens suggested the presence of porphyrins in all stages of blood staining, including the edematous cornea. Oxyhemoglobin was found in red-stained corneas, while methemoglobin was present in the brown-stained corneas. It was concluded that endothelial degeneration uniformly accompanied corneal blood staining in this model and that keratocytes are actively involved in hemoglobin degradation.

Pigmented Conjunctival Cysts Following Tetracycline/Minocycline Therapy

Unpigmented and pigmented cystic epithelial inclusions were found bilaterally within the lower palpebral conjunctiva temporally of a 31-year-old man. He had a history of tetracycline/minocycline therapy for 14 years because of acne vulgaris. The cysts were studied by light and electron microscopy, histochemistry, and ultraviolet light. By light microscopy the unpigmented cysts contained faintly eosinophilic globular material that disclosed yellowish-green autofluorescence indicating the presence of tetracycline/minocycline. The pigmented cysts revealed laminated eosinophilic to brownish concretions that also showed yellowish-green autofluorescence. Autofluorescence, however, decreased with increasing brown pigmentation of the concretions. Histochemically, the pigment, which failed to show the staining characteristics of lipofuscin, melanin or iron, probably represented an oxidation product of tetracycline. By electron microscopy the cysts contained moderately electron dense amorphous material as well as degenerating epithelial cells. The epithelial cells lining the conjunctival cysts, did not contain membrane-bound, large, pigment granules within their cytoplasm as has been demonstrated in the colloid and follicular epithelium of the thyroid following minocycline therapy.

Blood staining of the cornea: A histopathologic analysis of 16 cases

Sixteen eyes with corneal blood staining were examined by light microscopy. Two corneal buttons were also studied by electron microscopy and immunohistochemistry. By light microscopy, most eyes disclosed hyphema, angle-closure glaucoma, and endothelial attenuation with marked corneal edema. Extra- and intracellular hemoglobin particles as well as intracellular hemosiderin were found mostly in the central cornea. Frequently we observed a gradient of hemoglobin degradation from the posterior to the anterior corneal stroma with extracellular hemoglobin particles being more concentrated posteriorly while hemosiderin-laden keratocytes predominated anteriorly. By electron microscopy, moderately electron-dense, amorphous material consistent with hemoglobin was found extracellularly as well as incorporated into stromal keratocytes, while highly electron-dense, membrane-bound granules, consistent with hemosiderin, were found intracellularly. There was marked necrosis of keratocytes, mainly those that were overloaded with hemoglobin. We conclude that hemoglobin diffuses into the corneal stroma across an intact Descemets membrane. Continuous overload with hemoglobin leads to necrosis of keratocytes and irreversible corneal blood staining.

Applications of Immunohistochemistry to Ophthalmic Pathology

Immunohistological techniques have been increasingly used, both in general and ophthalmic pathology, for identification of specific cell types that may not be possible on morphological grounds or by conventional histochemical methods alone. Enzyme conjugate techniques using the peroxidase-antiperoxidase (PAP) immune complex method and the avidin-biotin-horseradish peroxidase method (ABC) are particularly useful as they are highly sensitive, provide permanent results, allow the use of paraffin-embedded tissues and do not require a fluorescent microscope. Antibodies against glial fibrillary acidic protein (GFAP), factor VIII-related antigen, muramidase, S-100 protein, myoglobin, prostatic acid phosphatase and prostate-specific antigen are valuable tools in surgical pathology and their applicability to ophthalmic pathology have been clearly demonstrated.