Ординатура / Офтальмология / Английские материалы / Veterinary Ocular Pathology A Comparative Review_Dubielzig, Ketring, McLellan_2010

subsequent immune-mediated inflammation of the endothelium

■Endothelial inflammation can be due to the natural infection with CAV-1 or, historically, was related to vaccination with the attenuated strain

■‘Blue eye’ may be unilateral, or bilateral

■There are anecdotal reports of sporadic cases of ‘blue eye’ encountered following vaccination with CAV-2 strains

•Malignant catarrhal fever (MCF) (Fig. 8.32)

■MCF is a bovine disease with high mortality that is caused by alcelaphine herpesvirus-1 or ovine herpesvirus-2

■Corneal edema associated with endothelial cell inflammation is a feature of both African Wildebeest-associated MCF and American Sheep-associated MCF.

CORNEAL NEOPLASIA

Canine corneal squamous cell carcinoma in dogs with chronic keratitis (Figs 8.33, 8.34)

•Corneal neoplasia is relatively uncommon in dogs

•There are 28 cases of squamous cell carcinoma (SCC) or carcinoma-in-situ in dogs in the COPLOW collection

•Affected dogs in our series have a history of chronic keratitis

•Most cases are in brachycephalic breeds and Pug dogs are the most frequently affected.

•Affected dogs are typically middle-aged and older

•Most are low-grade carcinoma or carcinoma-in-situ, involving predominantly the axial cornea.

•Morphologic features in these cases include:

■A raised mass lesion in the axial cornea

■Abrupt margins between a well-organized epithelium, with no dysplastic or anaplastic features, and the raised mass with disorganization, dysplastic epithelial features and cellular features of anaplasia

–If the neoplastic features are entirely contained by the basal lamina and do not infiltrate the stroma, these are carcinoma in situ

–If the neoplasm invades the stroma then it is considered squamous cell carcinoma

■In almost all cases the neoplastic tissue is confined

to the superficial stroma and lamellar keratectomy, with or without adjunctive therapy, is usually a successful treatment.

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A B

C D

Equine stromal-invasive squamous cell carcinoma (Fig. 8.35)

•There are eight cases of equine stromal-invasive SCC in the COPLOW collection

•This neoplasm is a variant of a limbal conjunctival SCC (discussed in detail in Ch. 7) which infiltrates primarily into the corneal lamellar stroma, masquerading clinically as chronic stromal/interstitial keratitis

•Clinically, there is a progressive thickening and opacification of the affected stroma

•Although the majority of the neoplasm lies within the corneal stroma, in some cases tumor tissue may also be recognized in the peripheral corneal surface and/or the limbus.

Angiokeratoma (vascular endothelial cell tumor arising within the cornea) (Fig. 8.36)

There are rare cases of tumors of vascular endothelial origin arising within the cornea. The COPLOW collection has one case in a horse and one in a dog.

•Infiltration of the cornea by an adjacent limbal conjunctival vascular endothelial mass was not definitively excluded in either case, as serial sections were not examined

•The other possible mechanism by which these tumors might arise would be neoplastic transformation of new vessels associated with pre-existing corneal disease.

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Figure 8.30  Anterior chamber collapse syndrome. (A–C) Gross photographs of animals with anterior chamber collapse syndrome resulting from early life ocular trauma. The iris tissue is plastered against the posterior cornea obliterating the anterior chamber. (D) Subgross photomicrograph of a similar globe showing pigmented iris tissue plastered against the posterior cornea (arrows).

Canine viral papilloma (see Ch. 7)

•Young dogs are affected

•Occasionally the disease is limited to the cornea.

Epitheliotropic lymphoma

There are two cases of epitheliotropic lymphoma of the cornea in dogs in the COPLOW collection.

Comparative Comments

•Overall, corneal tumors in man are unusual

•Squamous cell carcinomas can present as a primary corneal tumor, and the cornea may be involved by pagetoid spread of sebaceous carcinoma from the eyelid

•Biopsies showing corneal intraepithelial neoplasia occasionally come to the eye pathology laboratory

•Although primary melanomas of the cornea have been reported, corneal invasion by malignant melanoma of the conjunctiva is more often seen.

DISEASES OF THE SCLERA

Staphyloma (Fig. 8.37)

There are 72 cases in the COPLOW collection.

•A partial or full thickness defect in the cornea or sclera lined by protruding uveal tissue

•Staphyloma, may occur as a congenital lesion in isolation but is more frequently associated with other congenital ocular defects, as discussed previously, in Chapter 3.

•Acquired staphyloma:

■Limbal staphyloma is frequently recognized in glaucomatous canine eyes (see Ch. 13)

–In our collection, affected globes are always heavily pigmented

–Dogs with glaucoma as a result of ocular melanosis are particularly prone to developing staphylomas

–The relationship between scleral thinning and ocular melanosis is not known

–The appearance of staphyloma is often mistaken for that of a neoplasm

■Staphyloma associated with scleritis (see below).

Granulomatous scleritis, necrotizing scleritis (Figs 8.38, 8.39)

There are 93 cases of granulomatous scleritis documented in the COPLOW collection.

•All but three of these are canine cases, and most were diagnosed in enucleated globes

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•The other three cases involved one cat and two birds

•Granulomatous scleritis can arise by extension of a nonspecific inflammatory process, e.g., orbital cellulitis or panophthalmitis. However, in these 93 canine cases, the diagnosis implies a specific destructive inflammation within the sclera

■Although, in humans, granulomatous scleritis is often seen in individuals with other autoimmune conditions such as rheumatoid arthritis, this has not been a consistent feature of reported canine cases

–No such relationship with documented autoimmune conditions has been seen in any of the cases in the COPLOW collection

■Necrotizing scleritis has been reported in dogs with Ehrlichiosis

•Clinical features of scleritis may include:

■Redness

■Variable degrees of ocular pain

■Mild exophthalmos

■Signs of secondary uveal inflammation

■Posterior segment lesions, e.g., retinal detachment

•The inflammation in scleritis always has a pronounced, granulomatous component characterized by the presence of histiocytes/tissue macrophages. In addition, there may be a suppurative component, i.e. necrotizing scleritis, or in chronic scleritis, a lymphoplasmacytic component may predominate

•A diagnosis of scleritis implies that the second eye is at risk of developing scleritis

■The clinician should be alerted to this important prognostic information, due to the potentially serious implications for vision

•The morphologic features of scleritis in dogs include:

■The affected area of sclera is usually thickened

–The thickened sclera is typically a solid white. These affected regions are infiltrated by granulomatous inflammation

–Any portion of the sclera may be involved

■More rarely, scleral thinning may occur. In these cases dramatic staphylomas may be recognized

–Scleritis with staphyloma is usually manifest by a lymphocyte rich infiltrate with fewer granulomatous foci

■Histologic features of scleritis include:

–Granulomatous inflammation

–Lysis or separation of scleral collagen

–Granulomatous vasculitis, which is a common but not universal feature.

Canine limbal melanocytoma (Figs 8.40, 8.41)

In the COPLOW collection, there are 214 cases of canine limbal melanocytoma, representing 4% of all canine neoplastic submissions and 10% of all canine tumors of melanocytic origin.

•German Shepherd dogs are over-represented and Labrador Retrievers are weakly over-represented in the COPLOW collection.

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■Based on inter-relatedness of affected dogs in one published study, a genetic predisposition to the development of ocular melanoma has been proposed for Golden and Labrador retrievers

•There is a small spike in occurrence in dogs less than 2 years old

•Limbal melanocytomas in dogs are almost always benign but they can be quite large

•Morphologic features of limbal melanocytoma include:

■They arise from the melanocytes which form a pigmented ring around the limbal sclera in normal, pigmented dogs

■Limbal melanocytoma is usually a solid mass that is composed of a uniform population of heavily pigmented round cells, with very few heavily pigmented spindle cells

■Often, biopsy samples submitted are made up of small fragments because the tumors are often just sampled for diagnostic purposes prior to cryosurgery or photocoagulation.

Feline limbal melanocytoma (Fig. 8.42)

•In the COPLOW collection, there are 46 cases of feline limbal melanocytoma, representing 1.7% of all feline neoplastic submissions and 3% of all feline tumors of melanocytic origin

•Feline limbal melanocytomas are believed to be benign

■However, apparent generalized metastatic disease has been reported in one cat following resection of limbal melanoma

•It is important to distinguish limbal melanocytoma from extra-ocular extension of uveal melanoma, or conjunctival melanoma (see Chs 9 and 7, respectively, for further discussion of these important differential considerations)