Case 170512-2

Twelve-year-old, female spayed, Cairn terrier.

Nine months prior to submission of the biopsy sample, the patient developed progressive exophthalmos and ocular discharge from one eye. Four months prior to submission the conditioned worsened and the patient developed corneal ulceration, severe blepharospasm, and scleral injection. Secondary glaucoma was suspected. An enucleation was eventually performed. At the time of surgery, a CT scan was also performed. The imaging indicated osteolysis of the dorso-medial aspect of the orbit.

Unrelated history includes reverse sneezing, asthma, allergic skin disease, and pyoderma.

One entire ocular globe is submitted with an irregularly shaped, soft to firm, nodular, pale-tan 3 x 3 x 2.8 cm mass that surrounds the optic nerve; the palpebral conjunctiva are also submitted. The jar also contains approximately 10, small, variably sized nodular pieces of pale-tan soft to firm tissue.

The slide includes a section of globe in which a large, unencapsulated, poorly demarcated, densely cellular, infiltrative neoplasm surrounds the optic nerve and extends to cut borders. Neoplastic cells variably form sheets, nests, or lobules that are separated by a dense collagenous stroma or existing adipose tissue. Occasionally, neoplastic cells form whorls. They are pleomorphic, and they are typically large, with variably distinct cell borders. The cells contain abundant glassy, eosinophilic cytoplasm, and have centrally placed oval nuclei with coarsely stippled chromatin and a single nucleolus. Occasionally intranuclear cytoplasmic invaginations are present. Two mitotic figures are present in 10 high-powered fields. There is moderate anisocytosis and anisokaryosis. There are multifocal areas of mineralization and a single island of chondrocytes within lacunae (osseous and cartilaginous metaplasia).

The optic nerve appears to be focally compressed. Throughout the neuropil, there are scattered swollen axons. The optic nerve head is markedly cupped and the retinal pigmented epithelium is segmentally hypertrophied. The inner layers of the retina are atrophied and indistinct. The iris and ciliary body are moderately infiltrated by large numbers lymphocytes and plasma cells. The subepithelial stroma of the cornea is infiltrated by large numbers of neutrophils and fewer lymphocytes. Numerous small caliber vessels are present in the center of the cornea, and the stroma is compressed (consistent with edema). The corneal epithelium is acanthotic and occasionally forms rete pegs; it is focally necrotic. There are multifocal serum lakes within the epidermis (bullae). Pigment is present in in the stroma in the region of the limbus. Multifocally, lens fibers are enlarged, with glassy, hypereosinophilic cytoplasm (cataracts).

Neoplastic cells demonstrate mild to moderate immunoreactivity for vimentin.

Orbital meningioma with optic nerve compression

Moderate segmental retinal detachment, inner retinal atrophy, and severe optic nerve cupping

Moderate, focally extensive, chronic neutrophilic keratitis with neovascularization, edema, bullae and acanthosis

Moderate, diffuse, chronic lymphoplasmacytic uveitis

Multifocal cortical cataracts

Orbital meningiomas are rare tumors. Key features of them include pseudoinclusions within the nuclei, invasion of surrounding adipose and skeletal muscle, compression rather than invasion of the optic nerve, cartilaginous and/or osseous metaplasia. Tumor cells may form characteristic whorls but this occurs infrequently. Neoplastic cells should be vimentin positive and cytokeratin negative. The tumors tend to be locally invasive but rarely metastasize.

In this case, the optic nerve is focally compressed and there is invasion of neoplastic cells into the surrounding adipose and skeletal muscle. Other changes within the eye are likely secondary to a retro-orbital, compressive mass or are incidental (e.g. the cataracts). The retinal detachment, inner retinal atrophy and optic nerve cupping are all reminiscent of glaucoma. However, in this case, those changes are probably secondary to optic nerve compression by the tumor.

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