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Sudden, painless lump behind dog's front leg. Should I see a vet?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 20 lbs

My dog has a lump behind his front leg. It popped up suddenly about a couple weeks ago, is about the size of a golf ball, and doesnt seem to be painful to him. It has not gone away, should he see a vet? It is hard to see but easy to feel. The lump starts where it starts to dip and ends where my fingers are, if you can see it. Not sure what all the possibilities of it being..

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2 Answers

Most Helpful Answer

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Answered By Ricardo Fernandez, DVM

Veterinarian, Veterinary Oncology Resident

Published on April 8th, 2018

Thanks for using Petco Pet Education Center, formerly Petcoach! This could be a benign or malignant growth. This is often differentiated by a test called a fine needle aspirate (FNA) which is a pain free, inexpensive and easy procedure which in most cases will help reach a diagnosis. Sometimes a biopsy is needed for a definitive diagnosis. I recommend that you have him evaluated by your veterinarian for further assessment and treatment. I am really hoping for something benign. Good luck and have a good day!

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    Answered By Andrea M. Brodie, DVM

    Veterinarian

    Published on

    This could be an abscess or a cyst or a swollen axillary lymph node. This definitely needs to be seen by a veterinarian. If it is an abscess it will need to be lanced and evacuated and antibiotics given. If it is a swollen lymph node then your vet needs to check for infection in the areas that are served by this lymph node as well as check other lymph nodes for swelling which could signify lymphoma. Please schedule an appointment with your veterinarian.

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