A challenging case: Conjunctival lymphoma in a cat - Veterinary Medicine
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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.



Figure 5
Histologic evaluation of the orbital contents confirmed a diagnosis of conjunctival lymphoma (Figures 5 & 6). Since the tumor was extensive, it was difficult to determine whether it originated in the orbit or the conjunctiva. The initial clinical presentation was consistent with a conjunctival tumor: a relatively slow progression and protrusion of the nictitating membrane and no forward globe displacement.1

Figure 6
The mass was composed of neoplastic lymphocytes, completely obscuring the periorbital tissue and extraocular muscles. These cells also invaded the conjunctiva and eyelids and completely filled the shrunken globe. The cells had scant cytoplasm and round nuclei with densely stippled chromatin and a single prominent nucleolus and were arranged as diffuse sheets among a fibrovascular stroma. The conjunctiva was also infiltrated by lymphocytes, plasma cells, and neutrophils, and there were areas of necrosis and hemorrhage. The orbital tissue was completely invaded by neoplastic lymphocytes. No Reed-Sternberg cells—large abnormal lymphocytes that may contain more than one large pale nucleus with a prominent nucleolus and that indicate Hodgkin-like lymphoma—were seen.

Immunohistochemical staining demonstrated that the cells were negative for CD3 T lymphocyte receptor and positive for CD79a B lymphocyte receptor, confirming the mass was a B-cell lymphoma.

The diagnosis was non-Hodgkin-like, apparent primary conjunctival lymphoma. The histologic examination results indicated that neoplastic cells remained in the orbit, so the chance of mass recurrence was high.


At a recheck examination two weeks after surgery, the owner reported that the cat was eating and was alert and playful. Repeat blood tests revealed normal serum chemistry values and a normal PCV (32%). The cat still had reticulocytosis (reticulocytes = 22,620/μl) and increased nucleated red blood cells (0.1 x 103/μl), suggesting that the anemia had been due to blood loss and that erythrocyte production was sufficient.

Since the tumor had been removed and the cat was doing well, treatment options for the lymphoma were discussed with the owner. It was recommended that a thorough check for metastases and testing for feline leukemia virus (FeLV) infection be done before definitive treatment plans were made. Two weeks later, FeLV and feline immunodeficiency virus (FIV) tests were done and the results were negative. Orbital palpation revealed a swollen area, which could have been a regrowth of the mass. Additional ultrasonographic and radiographic examinations were recommended.


Figure 7
Six weeks after surgery, orbital ultrasonography (Figure 7) showed a soft tissue mass measuring 29.5 mm in diameter. This mass was evaluated with color flow Doppler ultrasound and appeared to be well-vascularized (Figure 8). Cytologic examination of a fine-needle aspirate of the submandibular lymph nodes did not reveal neoplastic cells. Thoracic and abdominal radiographic examination results were normal. Abdominal ultrasonography revealed that the cat had hepatomegaly, splenomegaly, and possible degenerative changes in both kidneys; however, cytologic evaluation of fine-needle aspirates of the spleen and liver failed to show any neoplastic cells.

Figure 8
Since there was no evidence of systemic neoplasia, localized radiation therapy was recommended to treat the lesion recurrence. Because of financial constraints, the owner elected to monitor for tumor progression.


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