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Q&A: Should I Have My Dog's Lump Biopsied?

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

Do all lumps need to be biopsied?

Do all lumps need to be biopsied?

Cancer or Harmless Fat Deposit?

"My 11-year-old Maltese/Coton cross has a lump on his right side towards the back of his ribcage. He had a lump on the left front paw towards where it connects to his body a couple of years ago, and I freaked and brought him to the vet I use up here in Anchorage, Alaska. I paid a hefty sum (over 1K) to have it removed and they said it wasn’t cancerous.

This newer growth is not hard but just fatty-feeling and does not bother him much; someone I spoke to said her older dog got them and that they were harmless fatty deposits. Should I have it biopsied?" —Ray

Fatty Lipomas Are Typically Harmless

The only way to tell for sure what is inside a lump on the skin is by examining the cells under a microscope. From your description and the dog's age, it certainly sounds like a lipoma, which is a benign fatty tumor found in about 2% of all dogs seen. (1)

If it is a lipoma, they are not a problem unless they grow in an area that makes it difficult to move around, like in the underarm. They rarely break open and become infected.

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Fine Needle Aspirate vs. Biopsy

If you do decide to have your dog's growth examined by your veterinarian, all you should have to pay for is an examination and a fine needle aspirate so that the veterinarian or technician can examine the cells under a microscope.

A fine needle aspirate is less expensive than a biopsy since your dog will not need to be under anesthesia nor will the sample need to be sent to an outside lab.

Watch Out for Growth and Infection

The only way to tell for sure what kind of growth your dog has is by looking at the cells. If you do not plan on doing this soon, take a picture of the lump up against a ruler so that you can watch the size. If it seems to be growing, have it checked out. Also, if the growth breaks open, it will get infected and should be treated by your regular vet.


  1. O'Neill DG, Corah CH, Church DB, Brodbelt DC, Rutherford L. Lipoma in dogs under primary veterinary care in the UK: prevalence and breed associations. Canine Genet Epidemiol. 2018 Sep 27;5:9.

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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