ABSTRACT OF THE WEEK

Veterinary ophthalmology
Volume 21 | Issue 2 (March 2018)

Iridociliary cysts masquerading as neoplasia in cats: a morphologic review of 14 cases.

Vet Ophthalmol. March 2018;21(2):125-131.

Jessica A Fragola¹, Richard R Dubielzig², Ellison Bentley³, Leandro B C Teixeira⁴

¹ Comparative Ocular Pathology Laboratory of Wisconsin, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.; ² Comparative Ocular Pathology Laboratory of Wisconsin, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.; ³ Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.; ⁴ Comparative Ocular Pathology Laboratory of Wisconsin, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.

Abstract

OBJECTIVE:To report 14 neoplasia-free feline eyes enucleated for suspected intraocular neoplasia containing only iridociliary cysts. To analyze clinical findings that may have led veterinarians to suspect neoplasia in these globes.

PROCEDURES:The archives at the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) were searched to identify neoplasia-free feline globes enucleated for suspected neoplasia. Clinical data were obtained from medical records, veterinarian surveys, and COPLOW submission forms. All samples were examined grossly and histologically.

RESULTS:All eyes were free of neoplasia and contained one or more iridociliary cysts. Nine of 14 globes were enucleated by or based on the recommendation of a board-certified veterinary ophthalmologist. In eight of 14 cases, the submitting clinician listed melanoma as the only suspected diagnosis; in six of 14 cases, 'tumor' or 'mass' was listed. Clinical examination revealed a darkly pigmented intraocular mass in 11 of 14 cases. The mass was clinically perceived to be within the iris in seven of 14 cases. When examined histologically, 11 of 14 eyes contained multiple cysts, 13 of 14 contained multiloculated cysts, eight of 14 had a hyperplastic iris pigmented epithelium or cysts with thick black walls, and five of 14 had cysts prolapsed into the anterior chamber.

CONCLUSIONS:Although most iridociliary cysts in cats are easily diagnosed on clinical examination, a subset may be mistaken for neoplasia. In cases of suspected iris melanoma, iridociliary cysts should be considered as a differential diagnosis, especially if a mass appears to emanate from behind the iris, dyscoria is present, or if similar changes are noted in the contralateral eye.

Companion Notes

Retrospective report on iridociliary cysts masquerading as neoplasia in 14 cats

Introduction

- intraocular neoplasia in the cat

- most common diagnosis in enucleated globes submitted to authors’ lab

- feline diffuse iris melanoma (FDIM)

- accounts for 50% of all feline ocular neoplasms

- tentative diagnosis is often reached by the ocular examination

- no clinical sign is pathognomonic for FDIM

- occasionally, globes enucleated for suspected FDIM are tumor free

- appears diffusely within the iris

- as progressive pigmentation that increases over several months to years

- may infiltrate the ciliary body, sclera and iridocorneal angle

- reported metastatic rates: 19-62.5%

- survival rates vary with tumor spread

- FDIM confined the iris has the same survival rate as control cats

- cats with ciliary body involvement have a decreased survival rate

- cats with scleral extension have lowest survival rate

- in a 1 report the overall metastatic rate was 19%

- decreased survival rate found to correlate with the following:

- extrascleral extension

- choroidal invasion

- necrosis within the neoplasm

- mitotic index >7

- definitive diagnosis requires histopathology

- most commonly via enucleation

- feline iridociliary cysts

- these originate from pigmented epithelium of iris or ciliary body

- in a report on the clinical findings in 36 cats with iridociliary cysts

- cysts can be transilluminated

- frequently multiple or bilateral

- can be pigmented

- may be attached to the iris rather than free floating

- most commonly are at the ventral pupil margin

- rarely associated with secondary intraocular disease

(uveitis, cataracts, or glaucoma)

- globes with cysts are occasionally enucleated as presumed melanoma

Study design

- study samples: Comparative Ocular Pathology Laboratory of Wisconsin

- 14 neoplasia-free feline eyes enucleated for suspected intraocular neoplasia

- eyes contained only iridociliary cysts

- history & signalment

- median age of affected cats: 10 years with a range of 2-16 years

- Siamese cat, 1 case

- Persian, 1

- clinical signs (location of the mass not specified in 1 eye)

- mass perceived to be within the iris, 7 of 14 cases

- behind the iris, 3

- associated with anterior displacement of the iris

- in the pupil, 2

- either in or behind the iris, 1

- pigmented mass, 11 of 14 cases

- color of mass not noted, 3 cases

- dark iridal pigmentation is one of the hallmarks of FDIM

- iris hyperpigmentation, 5 cases

- mass did not transilluminate, noted in 6 cases

- transillumination was not specifically mentioned in other cases

- dyscoria, 10 of 14 (no mention of nature of dyscoria in 2 cases)

[dyscoria = abnormality in the pupil’s shape]

- mass affecting pupil dorsally, 1

- mass affecting pupil ventrally, 3

- mass affecting pupil nasally, 1

- mass affecting pupil temporally, 1

- mass affecting pupil ventronasally, 1

- mass affecting pupil dorsotemporally, 1

- similar lesions in contralateral eye, 2 cases

- 1 cat later developed ocular hypertension in remaining eye

- ocular hypertension resolved after cyst deflation

- clinical diagnosis of glaucoma

- not made in any globes prior to enucleation

- in 9 cases clinician specifically noted a lack of glaucoma

- enucleation after initial examination, 11 cases

- increase in size seen over time, 3 cases

- prompting enucleation

- procedure: records retrospectively reviewed

- data obtained from records, veterinarian surveys and submission forms

- all samples were examined grossly and histologically

Results

- all eyes were free of neoplasia

- all eyes contained 1 or more iridociliary cysts

- 9 globes were enucleated by or based on recommendation of a ophthalmologist

(board-certified veterinary ophthalmologist)

- in 8 cases, submitting clinician listed melanoma as the only suspected diagnosis

- in 6 of 14 cases, 'tumor' or 'mass' was listed

-clinical examination

- darkly pigmented intraocular mass, 11 of 14 cases

- clinically perceived to be within the iris, 7 of 14 cases

- histology

- multiple cysts, 11 of 14 eyes

- multiloculated cysts, 13 of 14

- hyperplastic iris pigmented epithelium or cysts with thick black walls, 8

- cysts prolapsed into the anterior chamber, 5

“… these cysts often have characteristics that may help distinguish them clinically from FDIM: they often appear as masses within the pupil and are more likely to be bilateral.”

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