Tumor of the Eye (Ocular Cancer) in Dogs

Published on
Last updated on
5 min read

Key takeaways

A tumor is a proliferation of cells resulting in uncontrolled tissue growth. Primary eye tumors originate from within the eye, and secondary tumors spread to the eye from somewhere else in the body.

  • Retroviruses, UV exposure, and genetics can predispose a dog to eye tumors
  • A full workup with diagnostic imaging is necessary to determine the stage of cancer, and a biopsy diagnoses the type of tumor
  • Tumors are categorized based on where it arises within the eye, its cell type, and its behavior
  • Treatment varies depending on the tumor type
  • Some tumors can be surgically removed, or treated with chemotherapy or laser surgery
  • Other tumors necessitate removal of the affected eye (enucleation)
  • The prognosis for tumors is generally guarded, and poor for secondary tumors
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A closer look: Tumor of the Eye (Ocular Cancer) in Dogs

Cancers of the eye are rare in dogs. The severity of the condition depends on whether the tumor is benign or malignant.

Some tumors begin development inside the eye, and cannot initially be seen. By the time a tumor becomes visible the cancer may have already progressed to a later stage, further impacting prognosis.

Uveal melanomas tumors are the most common eye tumors to affect dogs. They typically originate in the iris, and are usually (but not always) benign.

Ciliary body adenomas (benign) and adenocarcinomas (malignant) tumors are the second most common. The ciliary body is behind the iris and not visible to the naked eye, however as cancerous cells proliferate a tumor becomes visible.

All tumors require prompt veterinary assessment. Early diagnosis and treatment provide the best chance of a positive outcome.

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Risk factors

Ocular tumors are rare in dogs. They can be benign, developing slowly and not spreading from the eye, or malignant, developing quickly and spreading throughout the body, destroying other tissue in the process. The prognosis for malignant tumors is guarded, and these cases may be fatal.

Tumors can also result in secondary ocular conditions, such as glaucoma or uveitis.

A dog affected by malignant tumors may present with more general symptoms of serious illness.

Ocular tumors are usually unilateral in dogs so vision loss is not immediately noticeable.

Genetics, retroviruses, and UV exposure can all influence cancer susceptibility, but cancer cannot be described in a simple ‘cause to effect’ correlation.

Cancer is more common in middle-aged to older, mature dogs. Some breeds are more susceptible to certain kinds of tumor than others, such as pale-eyed dogs being susceptible to spindle-cell tumors.

Possible causes

Cancer may develop due to environmental or genetic factors, but the cause is often unknown.

There are a variety of primary ocular tumors, including:

  • Mast cell tumor (which are not exclusive to the eye)
  • Neuroectodermal tumors
  • Schwannomas of blue eyed dogs

Secondary ocular tumors occur when tumor cells from cancer elsewhere in the body spread to the eye.

Main symptoms

The most recognizable symptom of an ocular tumor is a growth or mass developing in the eye. It can appear over or under the iris and pupil, depending on the type of tumor. Tumors present in a variety of opaque colors: black, yellow, green, red, or as multicolored splotches.

Testing and diagnosis

Diagnostic imaging helps establish the general health of the dog, and determine the stage of the cancer. A biopsy determines the type of tumor. Blood tests may be indicated, and referral to a specialist (oncologist or ophthalmologist) may be beneficial.

Steps to Recovery

Treatment varies depending on the type of tumor. Sometimes it is possible to remove the tumor itself, or treat it with minimally-invasive laser eye surgery or chemotherapy. Other times removal of the eye provides the best chances for recovery.

Ocular tumors are lifelong, and their prognosis is variable to poor. In some instances the cancer can recur, even after successful treatments.

Eye removal is commonly indicated, which may remove all of the cancer cells but results in loss of vision. Fortunately, a dog can still live a full and healthy life, even with reduced vision.

Secondary tumors and other malignant cancers have a far more guarded prognosis, and may be fatal, even with aggressive treatment.


Early identification and treatment provides greatest chances for a positive outcome. Ocular tumors are not contagious.

Is Tumor of the Eye (Ocular Cancer) in Dogs common?

Ocular cancer is rare in dogs.

Typical Treatment

  • Eye removal
  • Tumor removal
  • Laser eye surgery
  • Chemotherapy

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