History
A 3-year-old 4.09-kg (9-lb) spayed female domestic shorthair cat was referred to a veterinary teaching hospital because of color change of the left iris. The color change was first noticed 2 months earlier by the referring veterinarian during routine examination and was not associated with clinical signs. Previous medical history was unremarkable, and the cat was not receiving any medications.
Clinical, Gross, and Clinicopathologic Findings
At the referral evaluation, the cat was bright and alert. Its eyes were apparently not painful, and there was mild enlargement of the mandibular lymph nodes. There were no other notable physical examination findings. Results of a neuro-ophthalmic examination were within reference limits for both eyes, indicating normal vision. Within the left iris, there was a vascular, fleshy mass at the 12 o'clock to 3 o'clock position (Figure 1); there was mild dyscoria, compared with the right pupil. The right eye had no signs of abnormalities in the anterior segment. Results of bilateral fundic examinations, tear production measurements, intraocular pressure assessments, and corneal fluorescein staining were unremarkable. The cat was referred to the hospital's internal medicine service for further evaluation of suspected systemic disease. Thoracic radiography revealed a mild bronchial pattern.
Photographs of the left eye of a 3-year-old cat that was evaluated because of a color change of the left iris, which had been noticed 2 months earlier and was not associated with clinical signs. A—The iris is thickened in the dorsolateral aspect from the 12 o'clock to 3 o'clock position over 30% of the iris surface. The thickened iris is pink, vascularized, and raised from the normal iris surface. B—Following dilation of the left pupil with tropicamide 1% ophthalmic solution, the lesion causes dyscoria and results in a reverse-D–shaped pupil.
Citation: Journal of the American Veterinary Medical Association 256, 12; 10.2460/javma.256.12.1327
When the cat was returned for additional diagnostic evaluation the following day, its rectal temperature was 41.2°C (106.2°F) and it had been lethargic and hyporexic overnight. The fever resolved following IV fluid therapy. Aqueous humor paracentesis of the left eye as well as abdominal ultrasonography was performed without the cat being sedated. Ultrasonography revealed an enlarged spleen with hypoechoic miliary nodules, multifocal lymphadenopathy, and incidental nephrolithiasis. Aspirate specimens of the liver and spleen were collected.
The cat was negative for FeLV antigen and anti-FIV antibody.a Quantitative results of a CBCb and serum biochemical profilec were within reference intervals; results of a complete urinalysis were unremarkable. Microscopic evaluation of a blood smear revealed small numbers of atypical lymphocytes as well as rare organisms that were consistent with Mycoplasma hemofelis. The organisms were confirmed to be M hemofelis on the basis of PCR assay results.d Paracentesis of the left eye yielded 0.15 mL of aqueous humor, which was replaced with 0.15 mL of balanced saline (0.9% NaCl) solution.
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→
Cytologic Findings
Cytologic evaluation of a concentrated preparation of the aqueous humor sample revealed 1% nondegenerated neutrophils, 81% small lymphocytes, 11% large mononuclear cells, 2% plasmacytoid cells, and 5% markedly atypical large round cells. The atypical large round cells were larger than neutrophils; each cell was characterized by a single large round to oval to reniform nucleus with stippled chromatin, a single large prominent nucleolus, and abundant deeply basophilic cytoplasm that occasionally contained fine punctate clear vacuoles (Figure 2) These cells were morphologically similar to the atypical cells observed in the peripheral blood smear. Findings for the liver aspirate specimens were nondiagnostic owing to low cellularity. The spleen aspirate specimens were of excellent quality and highly cellular; the cells present included predominantly small lymphocytes mixed with medium-sized cells and a low number of markedly atypical large round cells, which were morphologically identical to those identified in the aqueous humor (Figure 3) Erythrophagia by atypical cells was occasionally observed.
Photomicrographs of a cytocentrifuged preparation of aqueous humor obtained from the left eye by paracentesis. A—Notice the 2 small mature lymphocytes and large atypical round cells that are each characterized by a moderate amount of basophilic cytoplasm often containing a prominent perinuclear clear zone and a single round to indented to pleomorphic nucleus with coarse chromatin. Wright-Giemsa stain; bar = 20 μm. B—Higher-magnification view of a large atypical cell containing a single large prominent nucleolus in the aqueous humor preparation. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 256, 12; 10.2460/javma.256.12.1327
Photomicrographs of a direct smear preparation of a fine-needle aspirate specimen of the spleen obtained from the cat in Figure 1. A—The specimen is hemodiluted and contains small lymphocytes accompanied by a smaller number of large atypical cells and some peripheral blood leukocytes. Wright-Giemsa stain; bar = 10 μm. B—Occasional large lymphocytes have undergone erythrophagia. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 256, 12; 10.2460/javma.256.12.1327
Additional Laboratory Findings
On the basis of the gross ocular lesions and ultrasonographic and cytologic findings, a diagnosis of large cell lymphoma was considered most likely. The remaining aqueous humor sample and splenic aspirate specimens were submittede for PCR assay to detect antigen receptor rearrangements (PARR assay) to further substantiate the clinical diagnosis of lymphoma. The laboratory combined the samples for analysis, and results were negative. Because of the limited sensitivity of the assay for detection of antigen receptor rearrangements in cats (sensitivity of 60% as indicated on the report) and the strong clinicopathologic evidence in favor of the diagnosis, the working clinical diagnosis of lymphoma was retained.
Interpretation and Case Summary
Interpretation and case summary: large cell lymphoma in a cat.
Comments
The cat was referred to the hospital's oncology service. Given the high suspicion for lymphoma, a chemotherapy protocol involving cyclophosphamide, hydroxydaunorubicin (doxorubicin), vincristine, and prednisone (CHOP protocol) was initiated.1 Beginning immediately after paracentesis, the cat was also treated with prednisolone acetate solution and ciprofloxacin ophthalmic solution applied 3 times daily to the left eye. This ophthalmic treatment was continued for the first week, after which ciprofloxacin administration was discontinued and the frequency of prednisolone acetate solution application was decreased to twice daily. After 4 weeks of chemotherapy, a 90% decrease in the size of the iris mass was observed and interpreted as a positive treatment response. After 6 weeks of chemotherapy, recheck abdominal ultrasonography revealed resolution of the splenic nodules and the iris mass was no longer visible. Given the apparent complete response to treatment in the context of the limited sensitivity of the PARR assay in cats, continuation of the chemotherapy protocol was recommended. The cat completed 4 chemotherapy cycles (19-week CHOP protocol). The cat was also treated with doxycycline (5 mg/kg/d [2.27 mg/lb/d], PO) for 4 weeks because of the Mycoplasma infection. One week after the final dose of chemotherapy, the cat was examined because of severe hypokalemia, fever, and prerenal-renal azotemia and was kept in intensive care for 6 days. Differential diagnoses for the persistent hypokalemia included hyperaldosteronism or nephrotoxicosis secondary to doxorubicin administration.2 Euthanasia (sodium pentobarbital solution administered IV) was ultimately elected by the owner because of the cat's poor response to supportive treatment and the owner's concern for its poor quality of life. Following necropsy, histologic examination of the left eye and a bone marrow specimen revealed lymphoma affecting the ciliary body of the left eye and the bone marrow, indicative of stage V disease. As a result of treatment, there was minimal residual disease in the left eye with poor cell preservation and frequent nuclear fragmentation. Compromised cytomorphologic characteristics precluded specific tumor grading; however, the mitotic index in the iris was 6 mitoses/hpf (400×), which was most consistent with an intermediate-grade tumor.3 Mild to moderate multifocal corticointerstitial nephritis was identified, and there was a clinical suspicion that the doxorubicin treatment may have contributed to the renal changes. Lymphoma was not identified in the cat's spleen, possibly because of the previous treatment.
Although presumed solitary intraocular or conjunctival lymphoma in small animals has been reported rarely, most cases of ocular lymphoma represent a facet of systemic disease.4 Despite the presumption of systemic disease in most cases, the eye can be the first or most obvious source of clinical signs.5 Ocular changes associated with lymphoma were identified in 12 of 26 cats for which a diagnosis of lymphoma had very recently been made; half of the 12 cats had anterior uveitis, although cytologic assessments were not performed to determine whether neoplastic cells were present in the anterior chamber.6 A retrospective study of extranodal lymphoma in cats identified ocular lymphoma in 5 of 110 cats, including 4 cases of uveitis and 1 case of an iris mass; 1 additional case of an isolated retrobulbar lymphoma lesion was reported.1 In another retrospective evaluation5 of intraocular and periocular lymphoma in 6 dogs and 15 cats, 6 cats had intraocular lymphomas (5 cases of B-cell and 1 case of T-cell lymphoma, all with anterior uveal involvement) and 9 cats had periocular lymphomas (6 cases of B-cell and 3 cases of T-cell lymphoma). In addition to the presence of neoplastic cells in ocular structures, lymphoma can cause a breakdown of the blood-aqueous humor barrier, resulting in anterior uveitis.5,6 Because of the delicate nature of the structures of the eye and potential complications associated with collection of ocular specimens, it may be preferable to collect samples for cytologic and histologic analyses from other involved structures. However, when an eye is the most obvious affected tissue, it might be the preferred sample source.
For cats, the cytologic diagnosis of ocular lymphoma has largely been based on the results of evaluation of aqueous humor samples, but cells may not be present in the aqueous humor of all affected cats.7 On the other hand, in 1 study,4 variable numbers of large or reactive lymphocytes were present in the aqueous humor of cats that ultimately received a diagnosis of idiopathic uveitis or feline infectious peritonitis, although the aqueous humor samples from cats in that case series contained much larger proportions of neutrophils, compared with findings for the cat of the present report. Because of the heterogeneous populations of lymphoid cells in the aqueous humor and spleen aspirate specimens obtained from the cat, we sought to try to confirm the clinical interpretation of lymphoma with a PARR assay; however, the assay did not confirm the diagnosis. Potential causes for negative results in an otherwise confirmed case of lymphoma include mutations in rare V or J genes, genetic polymorphism, or somatic hypermutation in immunoglobulin genes.8 Alternatively, false negative results can occur when there are too few neoplastic cells relative to unaffected cells.7 The sensitivity and specificity for detection of feline lymphoma reported9 by the laboratory used in the case described in the present report are 60% and > 90%, respectively.
Cytologic diagnosis of lymphoma in cats can be more difficult than it is in dogs because of a higher frequency of feline cases that have more mixed lymphoid populations and because of a greater proportion of small and intermediate cell forms that are less amenable to definitive cytologic diagnosis.9 Unfortunately, other supplementary diagnostic tests such as the PARR assay are considerably less sensitive for detection of lymphoma in cats than in dogs (60% to 65% sensitivity for feline specimens vs 75% to 80% sensitivity for canine specimens), which limited options for noninvasive confirmation of a suspicion of lymphoma in the case described in the present report. In the cat of the present report, the combination of clinical, diagnostic imaging, and cytologic findings was considered sufficiently compelling to initiate chemotherapy, and the response of the ocular lesion to the CHOP protocol suggested that the diagnosis was correct. Although antemortem confirmation of lymphoma for this cat was not available, the recommendation to continue chemotherapy was based on the apparent complete clinical response and the known limitations of the PARR assay in cats. The clinical suspicion of lymphoma was corroborated at necropsy. Furthermore, the necropsy findings indicated that the cat had not been in complete clinical remission despite completion of chemotherapy. Another interesting finding in this case was the occasional presence of RBCs within atypical lymphocytes; similar observations have been reported rarely in cases of feline lymphoma and are of uncertain importance.11,12
Footnotes
SNAP Combo FeLV antigen–FIV antibody test kit, Idexx Laboratories, Westbrook, Me.
ADVIA 2120, Siemens Medical Solutions USA Inc, Malvern, Pa.
Beckman Coulter AU480, Brea, Calif.
Colorado State University Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colo.
Colorado State University Clinical Immunology Laboratory, Colorado State University, Fort Collins, Colo.
References
1. Taylor SS, Goodfellow MR, Browne WJ, et al. Feline extranodal lymphoma: response to chemotherapy and survival in 110 cats. J Small Anim Pract 2009;50:584–592.
2. Poirier VJ, Thamm DT, Kurzman D, et al. Liposome-encapsulated doxorubicin (Doxil) and doxorubicin in the treatment of vaccine-associated sarcoma in cats. J Vet Intern Med 2002;16:726–731.
3. Valli VE, Kass PH, San Myint M, et al. Canine lymphomas: association of classification type, disease stage, tumor subtype, mitotic rate, and treatment with survival. Vet Pathol 2013;50:738–748.
4. Wiggans KT, Skorupski KA, Reilly CM, et al. Presumed solitary intraocular or conjunctival lymphoma in dogs and cats: 9 cases (1985–2013). J Am Vet Med Assoc 2014;244:460–470.
5. Ota-Kuroki J, Ragsdale JM, Bawa B, et al. Intraocular and periocular lymphoma in dogs and cats: a retrospective review of 21 cases (2001–2012). Vet Ophthalmol 2014;17:389–396.
6. Nerschbach V, Eule JC, Eberle N, et al. Ocular manifestation of lymphoma in newly diagnosed cats. Vet Comp Oncol 2016;14:58–66.
7. Linn-Pearl RN, Powell RM, Newman HA, et al. Validity of aqueocentesis as a component of anterior uveitis investigation in dogs and cats. Vet Ophthalmol 2015;18:326–334.
8. Avery AC. Molecular diagnostics of hematologic malignancies in small animals. Vet Clin North Am Small Anim Pract 2012;42:97–110.
9. Colorado State University College of Veterinary Medicine & Biomedical Sciences. PARR FAQs. Available at: csu-cvmbs.colostate.edu/academics/mip/ci-lab/Pages/PARR-FAQs.aspx. Accessed Apr 17, 2018.
10. Burkhard MJ, Bienzle D. Making sense of lymphoma diagnostics in small animal patients. Clin Lab Med 2015;35:591–607.
11. Heinrich D, Sturos M, Smith K, et al. What is your diagnosis? Liver aspirate from a cat. Vet Clin Pathol 2016;45:513–514.
12. Carter JE, Tarigo JL, Vernau W, et al. Erythrophagocytic low-grade extranodal T-cell lymphoma in a cat. Vet Clin Pathol 2008;37:416–421.
