Overview of Tumors of the Iris and Ciliary Body in Cats
The uvea in the eye consists of three parts: the iris, which is the colored portion of the eye behind the cornea; the ciliary body, which is the tissue immediately behind the iris lying between the iris and the choroid; and the choroid, which is the vascular layer in the back of the eye that supplies nutrition to the retina. The iris and ciliary body make up the anterior uvea and the choroid is called the posterior uvea.
Below is an overview of Tumors of the Anterior Uvea in Cats followed by in-depth information including details about the diagnosis and treatment of this disease.
Tumors occurring in the anterior uvea involve the iris, ciliary body or both tissues. They may originate from cells within these tissues (primary tumors) or they may spread to the eye from other body sites (secondary tumors).
Melanomas are the most common primary uveal tumor. Cats most commonly develop a brown color change that affects much of the iris. This pigmentation of the iris may develop over several months to years and may remain flat rather than forming a mass. Melanomas of the iris may be benign or malignant, and with time, benign tumors may become malignant.
Other primary tumors include the a benign tumor of the ciliary body (ciliary body adenoma), a malignant tumor of the ciliary body (adenocarcinoma), and a tumor that arises from embryonic tissues of the eye (medulloepithelioma).
The most common secondary anterior uveal tumor is lymphosarcoma. Metastasis to the anterior uvea from any kind of malignant tumor is possible. A rare type of tumor in the cat is the development of a malignant sarcoma within the eye months to years after the eye has experienced some sort of penetrating injury. These sarcomas are highly malignant.
Advanced anterior uveal tumors in many animals lead to symptoms of eye pain and blindness due to the development of uveitis, bleeding within the eye (hyphema), glaucoma, and damage to nearby structures of the eye. Unlike dogs, most anterior uveal tumors in cats tend to be malignant.
What to Watch For
Physical symptoms of illness may be seen with secondary (metastatic) uveal tumors because these tumors originate in other body organs and are usually present in that organ for some time before they spread to the eye. Systemic signs that may be seen include:
Diagnosis of Tumors of the Anterior Uvea in Cats
Diagnostic tests for anterior uveal tumors often include:
If a tumor is suspected or confirmed on the eye examination, then further testing may be warranted and may include the following:
Treatment of Tumors of the Anterior Uvea in Cats
Medical treatment alone is not enough to treat primary anterior uveal tumors. In early stages of uveal lymphosarcoma (a metastatic tumor), chemotherapy may induce tumor regression and remission of the cancer in some animals. Response to medical treatment for all other secondary uveal tumors is generally poor.
The treatment of choice for most uveal tumors is removal of the eye (enucleation). Malignant tumors must be removed as soon as possible to prevent their spread to other tissues. Large benign tumors often cause damage to nearby structures, as well as glaucoma, and the eye generally needs to be removed.
One complicating factor is that it is not often possible to determine if the uveal tumor is benign or malignant just by its appearance. There are also no effective biopsy techniques that can be used for these tumors. The tumor may only be determined to be benign/malignant once the eye is removed and a thorough pathological examination has been performed. For this reason, it is often necessary to remove the eye just to play it safe in case the tumor is malignant.
Prior to removal of the eye, it is important to determine that other organs in the body are free of tumor. With the exception of lymphosarcoma, if there is evidence of tumor(s) in other areas of the body, then no treatment may be effective and euthanasia may need to be considered.
Home Care and Prevention
Any time the iris changes color or there is eye discomfort, your cat should be examined by your veterinarian. For surgical or medical treatment to offer the most successful outcome, time is of the essence.
There is no preventive therapy or care for most anterior uveal tumors. Primary tumors and most secondary uveal tumors develop spontaneously. Post-traumatic sarcomas can be prevented by early removal of eyes that have been blinded and deformed by penetrating injuries.
In-depth Information About Tumors of the Iris & Ciliary Body in Cats
The most common primary anterior uveal tumors include melanoma of the iris and ciliary body, and adenomas or adenocarcinomas of the ciliary body.
Melanomas are the most common primary uveal tumor. Cats most commonly develop a diffuse, flat melanoma of the iris that begins as progressive pigmentation (darkening) of the surface of the iris. This color change is often a slow process and may develop over several months to years. Several golden-brown pigmented spots or “freckles” may develop simultaneously on the iris that progressively enlarge, grow together and become irregular along their surfaces. The migration of cancerous pigmented cells (melanocytes) into the iris eventually causes the iris to thicken and the shape of the pupil may become distorted. The pupil often remains larger than the opposite normal pupil. Glaucoma may also develop.
Some melanomas lack the typical brown/black pigmentation and are pink/white in color. These are called amelanotic melanomas. All amelanotic melanomas are considered malignant.
All anterior uveal melanomas have malignant potential. Metastatic disease related to uveal melanoma is more commonly observed in the cat than in the dog. Metastasis may occur as late as one to three years after eye removal and usually involves the lymph nodes, lungs and liver.
Primary sarcomas of the eye may develop in cats months to years after an event of ocular trauma or injury. These tumors are highly malignant and necessitate immediate removal of the eye.
The most common secondary anterior uveal tumor is lymphosarcoma. Usually the lymphosarcoma in the eye is one component of widespread cancer throughout the body. It is rare for lymphosarcoma to appear in the eye alone. Other uveal tumors represent the spread of malignant tumors from some other location in the body, such as breast cancer, cancer of the kidney or cancer of the thyroid. Metastasis to the anterior uvea from any kind of malignant tumor is possible, although most metastatic tumors appear in the choroid rather than in the anterior uvea.
A few other ophthalmic diseases or conditions can mimic the symptoms similar to those observed with anterior uveal tumors. It is important to exclude these conditions before establishing a conclusive diagnosis.
In-depth Information about Diagnosis of Feline Tumors of the Iris and Ciliary Body
Veterinary care includes diagnostic tests and subsequent treatment recommendations, as outlined below:
Diagnostic tests are performed to determine if the anterior uveal tumor is confined to the eye or if other organs or body cavities are affected with tumor. The results of these tests help define what is the most appropriate treatment. These tests may include:
Medical treatment alone is usually not enough to treat primary anterior uveal tumors. Typically, the inflammation caused by the tumor expansion within the eye does not respond well to medical therapy.
In the early stages of uveal lymphosarcoma, chemotherapy may induce regression of the tumor and the cat may go into remission. However, eyes that develop secondary glaucoma from advanced lymphosarcoma may not respond as well to chemotherapy, and may remain painful and blind.
Response to medical treatment for all other secondary uveal tumors is generally poor and ultimately most of these tumors require that the eye be surgically removed.
Enucleation is the most common therapy for many anterior uveal tumors in the cat. Often these eyes are painful due to secondary glaucoma, uveitis or hyphema.
Home Care of Feline Tumors of the Iris and Ciliary Body
Optimal treatment for your pet requires a combination of home and professional care. Follow-up can be critical, especially if your pet does not improve rapidly.