Given the plethora of locations and types of neoplastic disorders of the canine and feline eye, this hour long lecture cannot
possibly do more than scratch the surface of this subject matter. We can divide the subject material by the following anatomic
locations: eyelid, conjunctiva and third eyelid, cornea/sclera, uvea, optic nerve, and orbit, and by species given the differences
in disease progression.
Eyelid neoplasia in dogs
Approximately 75%-85% are benign. Most present as brown proliferative or verrucous, usually slow-growing lesions involving
the lid margins and meibomian glands. Some may grow to be quite large (see lecture slide show). More than 50% of these masses
are sebaceous adenomas, epitheliomas, and adenocarinomas. Squamous papillomas (more papillary in appearance, may be viral
in origin and part of papilloma complex) and melanocytomas (Weimeraners and Vizlas appear to be over-represented) are the
next most common – approx 25%. Melanomas of the lid margin appear to behave in a benign fashion and are sensitive to excision
or cryosurgery in dogs. Ten such other tumor types have been reported such as histiocytomas (young dogs, pink circular masses,
that may spontaneously regress), fibromas, lipomas, mast cell, basal cell, and squamous cell tumors, but make up only 10%
or less. Small snip or 2-3mm punch biopsies from large infiltrative masses can provide a diagnosis if reconstructive blepharoplasty
is anticipated (greater than 1/3 lid length), or simple excision or cryotherapy of small proliferative and benign appearing
masses may be curative. Expect recurrence 10-15% of time. Performing histopathology on excisional procedures is recommended
as follow up treatment may be necessary. Surgical lid reconstruction will be addressed in our wet-lab. Needle aspirates of
lid masses are often non-diagnostic in dogs.
Feline: In general, unlike dogs, most of these tumors are malignant. Some such as SCC may metastasize to regional lymph nodes
and other organs (usually very late though – average 5 years for lid SCC in cats). The most commonly reported lid tumors in
cats are SCC (Graefe'sArchv245n8p1217-1220 ;VOv10n6p337-343), basal cell carcinoma, mast cell tumors, fibromas/fibrosarcomas,
hemangiosarcoma, melanoma, lymphosarcoma, adenomas, and peripheral nerve sheath tumors (VOv8n3p153-158 '05 Hoffman, Blocker,
Dubielzig). Apocrine gland hidrocystomas are benign cystic tumors that appear as multiple dark brown proliferative masses
around the lids, often seen in brachycephalic cats that can be excised if needed. (JAVMA 15;230(8):1170-3.;VO 7(2):121-5).
Needle aspirates, cytology, or biopsies of lid masses in cats prior to surgery is recommended given most are malignant and
this will help when deciding on the need for wide-surgical excision, or when pre-surgical treatments (radiation) may be necessary.
SCC's are usually locally invasive and ulcerative (vs. proliferative in horses and cattle) lesions in mostly white cats –
(13x more common than other colors) – surgical excision with wide margins and adjuvant radiation or cryotherapy is the most
successful treatment. Many other treatments reported in literature but less available to us (photodynamic therapy, radioactive
gold beads, etc).
Conjunctiva and third eyelid
Canine conjunctival neoplasms
Most are benign but can be locally aggressive.
Squamous papilloma (17%); Nodular granulomatous episcleritis (NGE) – 16%
Vascular neoplasia (hemangioma/hemangiosarcoma) – 15% ; Mast cell tumors – 6%
Nictitans adenocarcinoma – 5% ; Conjunctival melanomas 10-20%? (and many other less common types): Most melanomas are malignant
by morphologic criteria and can grow to be quite locally aggressive; most will recur elsewhere on the conjunctiva when removed,
but they seldom metastasize. Those on the palpebral conjunctiva are more likely to metastasize– but reports of metastasis
are lacking in the literature. Data obtained from Dr. Brian Wilcock.