My dog has a four-year-old brain-like lump on his leg. What is it?

Looking at the photo and considering your description of the progression of this, I would suspect that it is a growing mass. It could simply be a fatty lump such as a lipoma. Other possibilities would be a soft tissue swelling due to trauma, but this seems less likely considering the progression. I would head to the vet and get them to test the lump to see exactly what it is. If it is just a lipoma and not causing bother it should not need to be removed.

It may be a cyst or adenoma of the skin glands. It does not appear inflamed or irritated so I doubt chewing and licking it is the cause. Your vet can look at it and take a sample to confirm what it is

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! Sorry to hear about Toby but since he has had this growth for so long, I doubt it has much clinical significance. I would be worried about it if it started bleeding, changed in size (got bigger), changed in appearance/shape/consistency, etc. One thing about growths on legs is they are a lot easier to remove when they are small. Large growth removals often leave little skin to allow closure of the surgical wound. So even though it's been there for a long time, I would consult with your veterinarian and see what they say. They may advise surgical removal due to the location for the reason I mentioned above. Good luck with Toby.

Without a physical exam or diagnostics, it is difficult to determine if this is something to worry over. Ideally, a fine needle aspirate or biopsy should be done to collect samples for pathology. This may provide a diagnosis. X-rays of the limb may be recommended to rule out bony involvement. Since you state it is growing, it should be removed before it becomes too large. As it is, that is a difficult area to close after a mass removal.

Osteosarcoma is typically a very aggressive cancer so it would be unusual for the pet to be doing well one and a half years later. There are many types of skin masses including benign bone growth. I recommend to play it safe and to have the mass aspirated by your veterinarian. This will give you a better idea of what’s going on and if it’s something that will cause a problem in the future or requires treatment. I hope this helps.

Thank you for providing a picture of Mia's lump! It could be a benign tumor, a cyst, or a malignant tumor. Unfortunately in a senior dog, there is always a chance it could be malignant. Any suspicious lumps should be examined by the vet. The vet can perform a test called a fine needle aspirate on it. To do this, the vet sticks a small needle into the lump to get a sample of it's cells, and examines the cells on a slide under a microscope. It's usually painless to the animal, and relatively quick to perform. I would take her into the vet in the next couple of days to have this lump examined and diagnosed so it can be treated as needed. Good luck, I hope this helps!

I can appreciate an increase in size/swelling above the right eye in your photos here. A brain tumor itself normally wouldn't cause a visible swelling, as the brain is encased in the bony skull and a tumor would just cause increased pressure on the brain but not cause changes in the shape of the skull. That being said, we can have bony tumors of the skull that can change the skull shape. We can also have tumors of the soft tissue (skin, muscle, connective tissue) that could be seen on the head, and also tumors of the eye/muscles behind the eye. Your dog should definitely have an examination done by the vet. They may recommend an aspirate of the swelling to help tell what is causing it, an x-ray of the skull, and possibly more advanced imaging like a CT scan. This problem may be something easily fixed or may be more involved, but we won't know without further testing.