Page 1323 - Clinical Small Animal Internal Medicine

1261

VetBooks.ir

138

Tumors of the Eye and Ocular Adnexa
1
Erin M. Scott, DVM, DACVO and Paul E. Miller, DVM, DACVO 2
1 Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA
2 Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin‐Madison, Madison, WI, USA

Tumors of the Ocular Adnexa Papillomas
In contrast, viral papillomas appear as verrucous masses
Tumors of the eye, orbit, or adnexa may be painful and originating from the conjunctiva in young dogs. They are
disfiguring, impair vision, and elicit concern that life‐ well demarcated, superficial, and grow rapidly. Surgical
threatening disease may be present elsewhere in the manipulation has been reported to disperse new papillo-
body. Even benign ocular tumors may cause blindness mas over the ocular surface. Papillomas, like histiocyto-
and loss of the eye simply by virtue of their location. mas, usually resolve spontaneously in young dogs,
Although both ocular and periocular tumors are report- although persistence in older dogs is common. Other
edly uncommon, their actual frequency is undoubtedly forms of benign papillomas in dogs include squamous
greater as most presumably benign ocular tumors, papillomas, which are of unknown etiology and occur
especially those affecting the canine eyelid, are not histo- at any age, as well as reactive papillomas, which are seen
logically examined. Histopathologic examination, however, secondary to other conditions that result in chronic
is essential to ensure proper diagnosis and treatment. irritation.

Squamous Cell Carcinoma
Eyelids, Third Eyelid, Conjunctiva, and Cornea Squamous cell carcinoma (SCC) has a predilection for
The etiology of ocular adnexal tumors is poorly understood the lower eyelid and medial canthus of white cats, and
but suspected causes include chronic inflammation, expo- comprises the majority of feline eyelid and third eyelid
sure to ultraviolet light, and viral infection (e.g., papilloma- tumors. It is less frequently reported in dogs, however, in
virus). In dogs, more than 85% of eyelid and conjunctival both species it tends to affect older animals. Predisposing
neoplasms consist of sebaceous or meibomian gland ade- factors include exposure to solar radiation, lack of
nomas and epitheliomas, papillomas, and melanomas. The adnexal pigmentation, and chronic ocular surface irrita-
substantial majority of these tumors are benign. Even histo- tion. Ocular surface SCC has a predilection for the lim-
logically malignant canine eyelid tumors rarely metastasize, bus, although it may also invade the cornea. SCC appears
although they may be more locally invasive and likely to as a focally thickened, roughened, pink‐to‐red lesion or
recur after surgery. In cats, however, most feline eyelid and as an ulcerated lesion which is slow to heal. Metastasis to
ocular surface tumors are malignant. regional lymph nodes occurs late in the course of disease
and distant metastasis is uncommon. SCC of the third
Meibomian Gland Adenoma/Epithelioma eyelid tends to more readily invade the orbit than ocular
Although rare in other species, benign meibomian gland surface or eyelid SCC (Figure 138.1a).
adenomas and epitheliomas are the most common eyelid
margin tumor in middle‐aged to older dogs. They may Hemangioma/Hemangiosarcoma
grow rapidly, first starting as a nodular swelling of the Adnexal vascular endothelial tumors are uncommon in
meibomian gland and eventually appearing as a prolif- dogs and rare in cats. As with ocular surface SCC, solar
erative mass exiting the meibomian gland orifice on the radiation is believed to be a risk factor. They usually
lid margin. arise from the nonpigmented conjunctiva of the lateral

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical