A challenging case: Conjunctival lymphoma in a cat

The owner's schedule and financial constraints made the cause of this cat's protruding nictitating membrane a challenge to diagnose and treat.

A 10-year-old 12-lb (5.5-kg) female spayed domestic shorthaired cat was presented to Colorado State University's Veterinary Medical Center for evaluation of a protruding nictitating membrane of the right eye. The cat's eye had not improved with topical gentamicin ophthalmic drops (1 drop b.i.d.) prescribed two weeks earlier by the referring veterinarian.


Vital Stats
The right eye had been blind and the cornea had been cloudy since birth. The cat had no history of other medical problems, and its vaccination status was current.

FIRST PRESENTATION

Physical and ophthalmic examinations

The results of a Schirmer tear test and tonometry were normal in both eyes, and there was no corneal staining with fluorescein dye in either eye.

The right eye had scarring and edema of the entire cornea, so the internal ocular structures could not be evaluated. The bulbar and nictitating membrane conjunctiva were moderately hyperemic, and the nictitating membrane protruded and covered about half the cornea. Retropulsion of the right globe was severely limited compared with the left eye. The cat appeared to be in pain.

The remainder of the physical examination findings were normal, and no enlarged lymph nodes were detected on palpation.

Presumptive diagnosis

We suspected that a right retrobulbar mass was present and recommended ophthalmic ultrasonography to further evaluate the eye. The owner failed to take the cat to the imaging appointment the next day.

SECOND PRESENTATION


Figure 1
The owner returned with the cat two months later. The right eye was extremely exophthalmic (Figure 1), the conjunctiva had severe chemosis and hyperemia, the eyelids were markedly swollen, and lagophthalmos was present. The conjunctiva was so swollen it covered most of the cornea and precluded corneal evaluation. The cat appeared to be in pain and resisted eyelid manipulation.

Differential diagnoses

Our two differential diagnoses were an extensive retrobulbar mass that was causing venous stasis in the eyelids and conjunctiva leading to swelling or a primary eyelid or conjunctival inflammatory or cellular infiltrate.


Figure 2
Cytologic evaluation of a fine-needle aspirate of the conjunctiva suggested an infiltrative lymphoma (Figure 2). Tropicamide, a topical anesthetic, was administered in both eyes, and orbital ultrasonography was performed to determine the extent of the lesion. The ultrasonographic examination revealed a mass that involved the right globe and the orbit (Figure 3). The mass was hypoechoic and irregularly shaped but had a definitive rounded region with hyperechoic edges and several anechoic cavitated regions. These findings suggested a neoplasm invading the ocular tissues. No abnormalities were identified on ultrasonographic examination of the left eye.


Figure 3
Given the extensive nature of the lesion, the cat's pain, and the owner's financial constraints, in addition to the fact that the eye was blind, immediate exenteration of the orbit was recommended. However, the owner did not return with the cat until three weeks later, reporting the mass had bled profusely several times during the previous three weeks. An exenteration was planned to remove the eye and the contents of the orbit.