Is the growth under the skin or visible to the naked eye?
If it is visible to the naked eye, then you will probably have noticed how long it's been there, and whether it's size has changed or not? If it's a lump, that is growing in size, then it could very well be a tumor that will need to be surgically removed. So if it's a visible growth, go to your local vet.
If the growth is under the skin, and you can feel that it is a hard lump, then - since you say your cat is very large - it could be the stomach or another major organ. Regardless, there is no way to know for sure. If this has come on suddenly, or if the animal is in pain, take it to your local vet so they cat run tests and do an ultrasound.
If it is visible to the naked eye, then you will probably have noticed how long it's been there, and whether it's size has changed or not? If it's a lump, that is growing in size, then it could very well be a tumor that will need to be surgically removed. So if it's a visible growth, go to your local vet.
If the growth is under the skin, and you can feel that it is a hard lump, then - since you say your cat is very large - it could be the stomach or another major organ. Regardless, there is no way to know for sure. If this has come on suddenly, or if the animal is in pain, take it to your local vet so they cat run tests and do an ultrasound.
