Page 699 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 32 Ocular Tumors 677

may appear as a focally thickened, roughened, and usually pink- of larger tumors aid in determining prognosis and planning defin-
to-red lesion in older animals or, more commonly, as an ulcer- itive therapy. Occasionally, orbital ultrasound, skull radiographs,
3–5
In contrast, papillomas
computed tomography (CT), magnetic resonance imaging
ated lesion with a protracted course.
VetBooks.ir in young dogs appear verrucous and usually progress rapidly over (MRI), regional lymph node cytology, and thoracic radiographs
weeks to a few months whereas they tend to be solitary and slowly
are required to localize or clinically stage potentially malignant
progressive in older dogs. Conjunctival MCTs often have smooth tumors such as SCC, MCTs, adenocarcinomas of the third eyelid,
surfaces and appear tan or red in color. Nonneoplastic conditions and conjunctival melanomas.
such as nodular granulomatous episcleritis, which is an inflamma-
tory disorder, can be mistaken for neoplasia. Therapy
In addition to a mass lesion, other clinical signs of eyelid or
ocular surface tumors may include epiphora, conjunctival vascu- Specific therapy varies with the type of tumor; its location, size,
lar injection, mucopurulent ocular discharge, protrusion of the and extent; whether the eye still has useful vision; the animal’s
third eyelid, conjunctival/corneal roughening or ulceration, and expected lifespan; the degree of discomfort the mass is creating;
corneal neovascularization or pigmentation. Occasionally, palpe- and the owner’s financial limitations. All eyelid tumors, whether
bral conjunctival masses protrude only when their bulk no longer benign or malignant, have the potential to affect vision or ocular
can be accommodated by the space between the eyelid and globe, comfort. Indications for tumor removal include any eyelid tumor
and very advanced tumors may create exophthalmia or enophthal- in a cat, rapid growth, ocular surface irritation, impaired eyelid
mia if the orbit is invaded. Large tumors and sebaceous adenomas function, owner concern, or an unappealing appearance. In young
often have a substantial inflammatory component and may be dogs, observation of nonirritating papillomas or histiocytomas,
secondarily infected. Mesenchymal hamartoma appears to have a even if quite large, may be appropriate as spontaneous regression
24
predisposition for the skin of lateral canthus of dogs. is common.
Tumors involving less than one-fourth to one-third of the
Diagnostic Techniques and Workup length of the eyelid are best treated by a V-plasty (wedge) or four-
sided excision. The latter technique affords superior apposition
25
In addition to fluorescein staining and examination of the ocular of the eyelid margins and wound stability, especially in tumors
surface with a cobalt filter or black light, the extent of involvement approaching the one-fourth to one-third limit, because the initial
of the bulbar and palpebral conjunctiva should be determined by incision is made perpendicular to the eyelid margin rather than
everting the eyelid (and third eyelid if affected). Careful palpation obliquely. In general, only one-third to one-fourth of the eyelid
of the lesion by inserting a lubricated finger in the conjunctival in dogs and one-fourth of the eyelid in cats can be removed with
cul-de-sac can be invaluable for determining the full extent of the these techniques. Antibiotic or antiinflammatory therapy may
tumor and whether bony involvement has occurred. Nasolacrimal reduce the size of large tumors that are infected or inflamed so that
lavage and possibly positive contrast dacryocystorhinography may a wedge or four-sided excision becomes possible. Electrosurgical
help characterize medial canthal masses. In general, small eyelid excision should be avoided because it may result in substantial
and ocular surface tumors are best diagnosed and treated by exci- scarring of the eyelids. Carbon dioxide (CO ) laser ablation may
2
sional biopsy. Fine-needle aspiration (FNA) or incisional biopsies be appropriate for some tumors. 26
Tumors greater than one-fourth to one-third of the eyelid typi-
cally require more advanced reconstructive blepharoplasty or use
of other therapeutic modalities. Some tumors may be responsive
to systemic chemotherapy (e.g., lymphoma, MCTs), local infiltra-
27
tion with chemotherapeutic agents such as cisplatin (e.g., SCC),
and/or local radiation therapy (RT; e.g., SCC). In some cases,
these modalities will completely eliminate the tumor or shrink
it to the point in which a less extensive surgical procedure can
be performed. Reconstructive blepharoplasty, however, is the pro-
cedure of choice if surgical cure is a possibility and these other
modalities have failed or are unlikely to substantially affect the
tumor or if the nature of the tumor indicates extensive margins
are required.
Cryosurgery is an attractive alternative to extensive blepharo-
plasty and has been reported to be effective in several canine eyelid
tumor types (see Fig. 32.2; see also Chapter 10). 2,28 It is quick,
less technically demanding than reconstructive blepharoplasty,
and usually permits preservation of the nasolacrimal puncta and
canaliculus. In many old or debilitated patients, cryosurgery can
be accomplished with only sedation or local/topical anesthesia.
After pretreatment with dexamethasone (0.1 mg/kg intravenous
[IV]), the mass is isolated with a chalazion forceps (if possible) and
debulked flush with the lid margin. Using liquid nitrogen and a
closed probe that approximates the diameter of the mass as much
as possible, a double freeze-thaw is performed so that the ice ball
extends 3 to 5 mm beyond the visible margins of the mass. Ice
• Fig. 32.3 Hemangiosarcoma of the third eyelid in a dog. balls should overlap in large tumors. Freezing may be repeated a