Page 1324 - Clinical Small Animal Internal Medicine

1262 Section 11 Oncologic Disease

(a) Adenoma/Adenocarcinoma
VetBooks.ir gland of the third eyelid. They appear as a localized, firm,
Adenocarcinomas are the most common tumor of the
smooth, pink swelling arising from the posterior surface
of the nictitans. They mimic prolapse of the gland of the
nictitans (i.e., cherry eye), but a key differentiating fea-
ture is their occurrence in older dogs and cats. Recurrence
is common if the entire gland is not removed, and metas-
tasis, especially to the regional lymph nodes and orbit, is
possible.

History and Clinical Signs
(b)
In addition to a mass lesion, other clinical signs of eyelid
or ocular surface tumors may include epiphora, conjunc-
tival vascular injection, ocular discharge, elevation of the
third eyelid, conjunctival/corneal erosion or ulceration,
and corneal vascularization or pigmentation. Palpebral
conjunctival masses often protrude when they no longer
can be accommodated by the space between the eyelid
and globe. Advanced tumors invading the orbit may
result in exophthalmia or enophthalmia, depending on
their location. Large tumors and sebaceous adenomas
often have a substantial inflammatory component and
Figure 138.1 (a) Squamous cell carcinoma involving the third
eyelid of a cat. Note the proliferative and ulcerated mass may be secondarily infected.
extending from the anterior surface of the third eyelid.
(b) Hemangioma of the third eyelid of a cat. Note the bright red,
exophytic mass extending from the leading edge of the third Diagnosis
eyelid. Source: Courtesy of University of Wisconsin‐Madison The extent of conjunctival involvement should be deter-
Comparative Ophthalmology Service Collection.
mined by everting the eyelid (and third eyelid if affected).
Careful palpation of the lesion by inserting a lubricated
finger in the conjunctival cul‐de‐sac can aid in deter-
limbus or leading edge of the third eyelid and appear as mining the full extent of the tumor and whether bony
relatively superficial, focal, raised, soft, red masses involvement has occurred. Nasolacrimal lavage and
with visible feeder vessels (Figure 138.1b). Ulceration possibly positive contrast dacryocystorhinography may
is common in larger masses. Metastasis of primary help characterize medial canthal masses. Fluorescein
conjunctival vascular tumors, even when classified as staining should be used to determine the integrity of the
hemangiosarcoma, is rare although it may recur fol- ocular surface.
lowing simple excision. It is critical to differentiate a Small eyelid and ocular surface tumors are best
primary ocular hemangiosarcoma from a metastatic diagnosed and treated by excisional biopsy. Fine
lesion. needle aspiration (FNA) or incisional biopsies of
larger tumors aid in determining prognosis and planning
Melanocytoma/Melanoma definitive therapy. Orbital ultrasound, skull radio-
Dermal melanocytic tumors of the eyelid are common graphs, computed tomography (CT), magnetic reso-
and typically benign in dogs, while in cats they are rare nance imaging (MRI), regional lymph node cytology,
and more malignant. Melanocytic tumors of the con- and thoracic radiographs may be required to localize
junctiva are infrequent and malignant in both species or clinically stage potentially malignant tumors such
(although distant metastasis tends to be uncommon). as SCC, third eyelid adenocarcinomas, and conjunctival
Conjunctival melanomas involving the nictitating melanomas.
membrane and superior palpebral conjunctiva may have
greater metastatic potential. In both cats and dogs, Therapy
conjunctival melanomas often locally recur following
surgical excision, and may invade the orbit and spread to Specific therapy varies with tumor type, size, location,
regional lymph nodes or lungs. and extent; whether the eye still has vision; the animal’s