Page 705 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 32 Ocular Tumors 683

clinical decline. Unpublished data from the COPLOW labora- effect on the prognosis of the disease. Dogs younger than 4
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tory indicates that dogs diagnosed with histiocytic sarcoma in the years old diagnosed with COR had high rates of recurrence and/
or metastasis and were euthanized within 6 months (median 2.5
eye have an average survival time of 3 months. Common pre-
VetBooks.ir sentations include severe uveitis, glaucoma, retinal hemorrhages, months). On the other hand, COR in dogs 6 years of age or older
hyphema, conjunctivitis, and keratitis characterized by corneal
had a less aggressive biologic behavior with no clinical signs of
infiltrates, edema, vascularization, and intrastromal hemor- recurrence or metastasis 8 to 13 months postdiagnosis.
rhage. 74,79–81 Exophthalmia resulting from orbital invasion by the Lobular orbital adenomas are made up of multiple soft fri-
tumor and vision loss due to optic nerve or central nervous sys- able lobules in the anterior orbit, making complete surgical exci-
tem (CNS) disease may also be present. Posterior segment lesions sion difficult. We have noted that for this tumor, excision of
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may include retinal vascular tortuosity, papilledema, multiple the multiple soft masses is possible with a large diameter surgi-
intraretinal hemorrhages, and retinal detachment. In one study, cal suction tip or a Sims Connector. This increases the ability to
the lifespan of dogs with intraocular lymphoma was only 60% to completely remove the tumor and limits the surgical exposure
70% as long as dogs without ocular involvement when treated required.
with cyclophosphamide, vincristine, and prednisolone (COP), or
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with doxorubicin. Topical or systemic corticosteroid therapy or History and Clinical Signs
enucleation is palliative. (See Chapter 33 for the definitive ther- Slowly progressive exophthalmia, absent to minimal pain on open-
apy of lymphoma.) Ophthalmic disease, especially intraocular or ing the mouth, difficulty in retropulsing the eye, and deviation of
retinal hemorrhage, may also be the presenting complaint in ani- the globe typify orbital neoplasia. Sudden erosion of nasal or sinus
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mals with multiple myeloma. tumors into the orbit occasionally results in acute exophthalmia
and substantial orbital pain. Enophthalmia may occur if the mass
Tumors of the Orbit and Optic Nerve is anterior to the equator of the globe. Lobular adenomas may
present as soft, raised, subconjunctival masses and create either
Incidence and Risk Factors enophthalmia or exophthalmia. Chronic epiphora secondary to
Risk factors other than middle to old age, possibly large-breed obstruction of the nasolacrimal duct, exposure keratoconjunc-
dogs, and possibly sex (female dogs, male cats) have not been tivitis, palpable orbital masses after enucleation, or unexplained
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described. 84–92 Tumors involving the optic nerve are rare, although orbital pain also suggests orbital neoplasia. 84–87 Measurement of
secondary invasion occurs in feline posttraumatic sarcomas, feline corneal diameters and intraocular pressure (IOP) aids in differ-
SCC, and canine choroidal melanomas. Canine orbital meningi- entiating glaucomatous ocular enlargement (large corneal diam-
oma is the most common tumor of the optic nerve but comprises eter, high IOP) from exophthalmia (normal corneal diameter and
only 3% of all meningiomas in dogs. 88,90 Orbital rhabdomyosar- IOP).
coma is a relatively rare but highly malignant neoplasm in juvenile Optic nerve lesions may result in unilateral or bilateral blind-
dogs that accounts for 0.2% of all canine tumor submissions in ness (the latter if the optic chiasm is affected), optic nerve head
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the COPLOW database. Lobular adenomas of unspecified glan- pallor, papilledema, or marked protrusion and congestion of
dular origin have been recently reported to involve the anterior the optic disc on ophthalmoscopy. A relatively mild degree of
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orbit in dogs. exophthalmia with vision loss suggests optic nerve neoplasia
because tumors of other orbital tissues typically cause profound
Pathology and Natural Behavior exophthalmos before visual loss. Tumors affecting the retrobul-
Orbital neoplasia may be primary (most common in dogs), sec- bar, intracanalicular, or chiasmal portions of the optic nerve may
ondary to extension of adjacent tumors into the orbit (most com- not result in exophthalmia or a visible change in the optic nerve
mon in cats), or the result of distant metastasis. In cats and dogs, head.
more than 90% of orbital tumors are malignant, and regional
infiltration (including into the CNS) or distant metastasis is com- Diagnostic Techniques and Workup
mon. 84–87 At least 26 types of orbital tumors, roughly equally It is essential to differentiate nonneoplastic orbital inflammatory
divided among connective tissue, bone, epithelial, and hemo- diseases (granulomas, cellulitis, abscesses, myositis of the extra-
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lymphatic origins, have been reported in dogs. Osteosarcomas, ocular and masticatory muscles) from neoplasia. Animals with
MCTs, histiocytic sarcomas, fibrosarcomas, and neurofibrosarco- inflammatory disease typically exhibit significant pain on opening
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mas are the most common canine primary orbital tumors. More the mouth. The location of an orbital mass can usually be deter-
than two-thirds of feline orbital tumors are epithelial in origin, mined by careful physical examination, including retropulsion of
with SCC being the most common, but at least 15 other tumor the globe, oral examination caudal to the last molar, and determi-
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types have been described in cats. nation of the direction of malposition of the eye.
Canine orbital meningiomas exhibit predictable biologic In addition to physical examination, cytology of regional lymph
behavior. They are slowly progressive and rarely metastasize; they nodes, orbital ultrasound, orbital and thoracic radiographs and
may be osteolytic and invade surrounding tissues, including the orbital CT/MRI imaging should be considered. In one study of
CNS via the optic foramen. 87,89,90 Primary optic nerve tumors cats with orbital neoplasia, 59% had radiographic signs of orbital
in dogs include glioma and meningioma. 87,88,90,91 Retinal and bone lesions and 15% had evidence of metastasis on thoracic
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optic nerve gliomas may be considered as differential diagnoses of radiographs. CT or MRI offer superior depictions of the orbit
intraocular and orbital masses. The metastatic potential of gliomas and facilitate planning of either radiation or surgical therapy (Fig.
appears to be low, but ascending invasion into the ventral aspect 32.8). Histologic characterization by FNA or needle core biop-
of the brain is possible. 92 sies (performed via the mouth or through the orbital skin), with
Canine orbital rhabdomyosarcomas (COR) are embryonal ultrasound or CT guidance if necessary, are helpful in arriving at
tumors that usually exhibit an aggressive biologic behavior. A a definitive diagnosis. The globe, major orbital blood vessels, and
recent case series reported that the age of the patient had a direct optic nerve should be avoided. Because 50% of orbital tumors