Cancerous Eye

Good week for reader questions! Here's one from Darlene.

Our cat, Tig, is a 13 year old (indoor only) domestic short haired cat. She has been in very good health until the last month or so. We began to notice the color of her iris began to get darker. In addition, sometimes her pupil began to stay open wider than the other pupil in the other eye. She has not shown any signs of pain. She does not wash that eye anymore and will let you pet her face near that eye. We recently took her to the vet to be examined.
They informed us she likely has an iris melanoma with glaucoma in that eye. They have recommended she have an enucleation procedure performed. They would have the eye sent to UGA to see if the tumors in the eye were Cancerous. We have become more comfortable with the removal of her eye. However, we are very concerned that if it is Cancerous, has it spread to her other eye or any other part of her? This has all happened so fast with the change in eye color just in a month so we are very concerned if it is cancer and if the cancer has spread.
Is there a way to screen her for cancer to find out if it is through out her body? I have attached her photograph. Sadly, if she does have cancer in the rest of her body we would not like to put her through the procedure removing her eye and the cost to us for only extended her life briefly.


All good questions, Darlene. I didn't include the pictures in this post because they weren't as clear as I would like, and it's hard to tell as much as I would like. But I can see some potential issues, including the darkening of the iris.

It wouldn't be possible to tell 100% for certain that this is a melanoma without sending tissue samples off, though this certainly sounds and looks like the main possibility. If a tumor is growing on the iris it can affect the outflow of fluid from the eye, leading to glaucoma. Glaucoma by itself is pretty serious and can lead to permanent blindness as well as being painful. Add a likely tumor to the issue and you have a bad situation. Either one of these problems alone could warrant removing the eye, and when you combine them the best solution is to have the surgery done.

Pets do very well with only one eye. It's a bit harder for cats because of the loss of depth perception, making it harder for them to judge distance when they're climbing and jumping. But they quickly learn how to compensate and live with the difference. I've removed many eyes myself, and certainly think it's a valid procedure and better than the alternative.

So let's talk about the other concern. What about metastasis (spread to other locations)? This is a valid question, and one that should be examined. However, there is no way to be completely certain that a tumor hasn't spread. All you can do is your best due diligence, examine as much as you can, and pray that there isn't anything hidden. Some tumors are small enough that we can't detect them with any means, and there aren't simple blood tests for most forms of cancer. In a situation like this you want to perform a full blood chemistry and blood cell count, looking for signs of organ abnormalities and alterations in the white blood cells. You also want to do chest radiographs as the lungs are a common place for tumors to spread. If these tests are normal, you've done the best you can to screen for cancer outside of going to a specialty clinic and having a CT or MRI performed on the pet.

If there are abnormalities, especially tumors in the chest, I would agree that major surgery like enucleation wouldn't help improve longevity and would be unnecessary. If everything is normal, I would recommend having the surgery done as soon as possible. There will always be the chance that something was missed on the screening and you may have tumors appear later, but that's a risk that everyone takes when dealing with cancer.

I hope this helps with the questions. Good luck!