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Q&A: What's This Bump on My Dog's Leg? Should I Be Worried?

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Dr. Mark is a veterinarian. He has been working with dogs for more than 40 years.

The only way to tell if a lump on a dog is cancerous is to do a biopsy.

The only way to tell if a lump on a dog is cancerous is to do a biopsy.

Is This Lump on My Dog's Leg Serious?

"We recently took in a stray with this lump on its leg. Is it serious? Does it need a biopsy to determine if it is an issue? We like the dog and want to keep it. But we don't take our animals to a vet for non-life-threatening issues. Just trying to see if it is." —Colleen

Histiocytoma in Dogs

If I had to guess, I would say that it was a histiocytoma—a benign lump that does not need any sort of treatment. The problem, though, is that you cannot tell if a growth is cancerous without removing some of the cells and looking at them under a microscope.

Histiocytoma vs. Mast Cell Tumor

Looking at the cells might also tell you that it is a mast cell tumor, which can look similar and definitely needs treatment. The link above shows a mast cell on a dog's leg.

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I would recommend that you take your dog in for an examination and a fine needle biopsy of the lump. If it is a histiocytoma, it is not life-threatening and nothing will need to be done about it. (If it grows too fast and irritates the dog, it can be frozen off easily.) If it is a mast cell tumor, the dog will need surgery and maybe chemotherapy.

Keep a Close Eye on the Lump

If you do not want to take the dog to a vet at this time, be sure to take a photo with your thumb up against it every month and see how it is growing.

If it is growing rapidly, ulcerates, or breaks open and starts leaking pus, you will need to take the dog to a vet to have the growth taken care of.

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2022 Dr Mark

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