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

sectioned in such a way that the lesions are isolated for histologic evaluation

•Eosinophils are seldom a prominent feature of ocular larval migrans in dogs

•A high degree of suspicion is warranted on finding unexplained retinal perivascular lymphocytic inflammation in young

dogs.

RETINAL NEOPLASIA

Primary neoplasms of the retina

These are rare in domestic animals. There are 13 cases of primary retinal tumors in dogs and two in cats in the COPLOW collection.

Comparative Comments

Concerning ocular inflammation attributable to infectious agents, the human retina is involved in instances of infectious endophthalmitis secondary to bacterial or fungal disease.

•Fungal infections of the retina occur in immunosuppressed human patients as a result of fungemia. The most commonly implicated fungi are Candida, Aspergillus, and Cryptococcus neoformans

•A number of viruses can affect the human retina, including herpes simplex, herpes zoster, cytomegalovirus, human immunodeficiency virus (HIV), rubella, and measles

–Herpes simplex, Herpes zoster and cytomegalovirus can cause a devastating destruction of the human retina, known as acute retinal necrosis.

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Canine retinal glioma (astrocytoma) (Figs 11.42, 11.43)

There are 10 examples in the COPLOW collection

•Although not common, GFAP-positive gliomas are the most frequently encountered primary retinal tumors in dogs

•Retinal gliomas most often arise in the central retina, near or continuous with the optic nerve

•Gliomas can have a bland or an anaplastic cellular profile (see Ch. 12). The anaplastic tumors are often extensively necrotic.

Retinal tumors with features of neural differentiation

Primitive neuroectodermal tumors (PNET), including medulloepithelioma and retinoblastoma (Fig. 11.44).

•PNET are usually in the peripheral retinal or continuous with the ciliary body

•PNET have been reported in a number of different species including dogs, horses and camelids

•Medulloepithelioma is characterized by the presence of thick tubular rosettes with a complex multi-cell lining and a distinct lumen. More simple Flexner–Wintersteiner or Homer–Wright rosettes may also be present in medulloepithelioma, but they are not the defining feature

■Most medulloepithelial tumors originate in the ciliary body or optic nerve, rarely in the retina

•Retinoblastoma in animals (Fig. 11.45)

■Most PNET tumors of animals do not satisfy the rather stringent criteria to be categorized as retinoblastoma. There is one canine case in the literature, which has been designated as a retinoblastoma using criteria developed in humans

■Retinoblastoma is a PNET of the retina with the following features:

–Poorly-differentiated, very primitive neural cells, with a large nucleus to cytoplasm ratio

–Simple rosette structures with characteristics of either Flexner–Wintersteiner or Homer–Wright

Flexner–Wintersteiner rosettes are characterized by a single layer of cells with apical tight junctions and a distinct lumen

Homer–Wright rosettes are characterized by a more primitive and less distinct structure with no tight junctions and an indistinct lumen

Although rosette structures are a frequent feature of retinoblastoma, their presence is not required to make the diagnosis

–Sparse vascularity and associated extensive tumor necrosis, except immediately around blood vessels

–Mineralization within human retinoblastoma is so common that it is a feature that is essential to make the diagnosis by ultrasound or CT scan.

Comparative Comments

•In humans, the most common primary intraocular malignancy of childhood is retinoblastoma. This tumor occurs in approximately 1 in 14 000–20 000 live births

•The tumor is composed of small dark cells, with hyperchromatic nuclei and scanty cytoplasm. Rosettes (Flexner–Wintersteiner and Homer–Wright) are characteristically seen

•A benign form of the tumor, known as retinocytoma, can occur

•Retinoblastoma is extremely rare in other species

•Other tumors of the human retina are uncommon and include massive gliosis of the retina, astrocytic hamartomas, hemangioblastomas, as well as adenomas and adenocarcinomas of the RPE.

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