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Neoplastic lesions can affect every tissue of the eye in both dogs and cats and can occur in the orbit, adnexal tissues (eg, eyelids, conjunctiva), and uveal and retinal tissues inside the globe.1

Orbital Tumors 

Orbital masses can cause exophthalmia with decreased ocular retropulsion, strabismus, periocular swelling, and elevation of the third eyelid (Figure 1, below). Although nonneoplastic processes (eg, cellulitis, salivary cysts) may occur, many orbital masses are neoplastic, with a reported frequency of 57.6%.2 Patients with cellulitis, such as that seen with a foreign body or orbital abscess, may present acutely and appear painful, whereas patients with neoplasia may have a more chronic history, typically with little discomfort until later stages of the disease process.

Common orbital neoplasms include carcinomas (eg, squamous cell carcinoma, adenocarcinoma), sarcomas (eg, osteosarcoma, fibrosarcoma), meningioma, and lymphoma.2   Tumors may extend from local tissues (eg, sinonasal cavities) or originate from the bony or soft tissue structures of the orbit; metastasis from distant sites occurs less often. Orbital mass diagnosis can be confirmed using a combination of imaging (eg, ultrasonography, CT, MRI) and biopsy sampling of associated tissues (Figure 2). Bony lysis is a common finding with many neoplasms.

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Adnexal Tumors 

Meibomian gland adenomas (Figure 3) are the most common eyelid tumor in dogs; in cats, squamous cell carcinoma is most prevalent (Figure 4).1,3 Other tumors that affect the eyelid or conjunctival tissues include papilloma (Figure 5), melanoma, hemangioma or hemangiosarcoma (Figure 6), and mast cell tumors (Figure 7). Adnexal tumors in dogs tend to be benign, whereas many eyelid neoplasms in cats have more malignant behavior.1,3

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Tumors of the Globe 

Limbal melanocytomas (Figure 8) are benign, heavily pigmented lesions that occur most commonly in German shepherd dogs and Labrador retrievers.4,5 These tumors can expand locally but do not invade the globe or metastasize. They are treated via surgical debulking with diode laser ablation.4

The most common intraocular tumor in both cats and dogs is primary uveal melanoma (Figure 9).6,7 Although these tumors frequently exhibit nonmetastatic but potentially locally invasive behavior in dogs, a greater potential for metastasis is present in cats with iridal melanoma (Figure 10). Surgical removal of the globe is curative if metastasis has not occurred.

Other primary intraocular tumors include iridociliary body adenomas (Figure 11) and medulloepitheliomas. Lymphoma is the most common secondary metastatic neoplasia seen in the eye (Figure 12).1,7 Lymphoma can present with anterior uveitis, chorioretinitis, panuveitis, diffuse iridal thickening, or a discrete uveal mass. Although peripheral lymphadenopathy or other systemic signs are often seen with multicentric lymphoma, ocular signs may be the initial presenting clinical sign.


References and author information Show
  1. Labelle AL, Labelle P. Canine ocular neoplasia: a review. Vet Ophthalmol. 2013;16 Suppl 1:3-14.
  2. Armour MD, Broome M, Dell’Anna G, Blades NJ, Esson DW. A review of orbital and intracranial magnetic resonance imaging in 79 canine and 13 feline patients (2004-2010). Vet Ophthalmol. 2011;14(4):215-226.
  3. Newkirk KM, Rohrbach BW. A retrospective study of eyelid tumors from 43 cats. Vet Pathol. 2009;46(5):916-927.
  4. Andreani V, Guandalini A, D’Anna N, et al. The combined use of surgical debulking and diode laser photocoagulation for limbal melanoma treatment: a retrospective study of 21 dogs. Vet Ophthalmol. 2017;20(2):147-154.
  5. Donaldson D, Sansom J, Scase T, Adams V, Mellersh C. Canine limbal melanoma: 30 cases (1992-2004). part 1. signalment, clinical and histological features and pedigree analysis. Vet Ophthalmol. 2006;9(2):115-119.
  6. Hendrix DVH. Diseases and surgery of the canine anterior uvea. In: Gelatt KN, Gilger BC, Kern TJ, eds. Veterinary Ophthalmology. 5th ed. Ames, IA: Wiley-Blackwell; 2013:1179.
  7. Stiles J. Feline ophthalmology. In: Gelatt KN, Gilger BC, Kern TJ, eds. Veterinary Ophthalmology. 5th ed. Ames, IA: Wiley-Blackwell; 2013:1511-1514.
  8. Pirie CG, Knollinger AM, Thomas CB, Dubielzig RR. Canine conjunctival hemangioma and hemangiosarcoma: a retrospective evaluation of 108 cases (1989-2004). Vet Ophthalmol. 2006;9(4):215-226.
  9. Kiupel M, Webster JD, Bailey KL, et al. Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors to more accurately predict biological behavior. Vet Pathol. 2011;48(1):147-155.
  10. Fife M, Blocker T, Fife T, Dubielzig RR, Dunn K. Canine conjunctival mast cell tumors: a retrospective study. Vet Ophthalmol. 2011;14(3):153-160.
  11. Kalishman JB, Chappell R, Flood LA, Dubielzig RR. A matched observational study of survival in cats with enucleation due to diffuse iris melanoma. Vet Ophthalmol. 1998;1(1):25-29.
  12. Wiggans KT, Reilly CM, Kass PH, Maggs DJ. Histologic and immunohistochemical predictors of clinical behavior for feline diffuse iris melanoma. Vet Ophthalmol. 2016;19 Suppl 1:44-55.

Georgina M. Newbold

DVM University of Tennessee

Georgina M. Newbold, DVM, is a comparative ophthalmology resident in the small animal clinical sciences department at University of Tennessee. Dr. Newbold earned her DVM from University of California, Davis, and was a 2014 student award recipient of the American College of Veterinary Ophthalmologists. Her areas of interest are feline keratitis and postphacoemulsification complications in dogs.

Diane Hendrix

DVM, DACVO University of Tennessee

Diane Hendrix, DVM, DACVO, is a professor of comparative veterinary ophthalmology at University of Tennessee, where she earned her DVM. Her primary research interests are infectious corneal diseases of all species and squamous cell carcinoma in horses. Dr. Hendrix completed a residency in comparative ophthalmology at University of Florida.

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