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My female dog has a lump on her breast. Is it mammary cancer?

Updated On September 23rd, 2025

Pet's info: Dog | American Bully | Female | unspayed | 6 years and 9 months old | 55 lbs

Hi: my name is Denise my fluffy daughter Moet Williams she has a big lump in one of her breast can you tell me what it may be Thank You Denise Williams

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3 Answers

Most Helpful Answer

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Answered By Linda G, MS, DVM

Veterinarian

Published on August 8th, 2020

Hello. The most likely cause for the lump on Moet is mammary cancer. You do want to have your veterinarian examine Moet as soon as possible & schedule her for surgery. Fortunately, breast cancer in dogs is not as aggressive as it is in women, so removing the tumor may be be curative for this site. Unfortunately, other tumors can turn up in other parts of the mammary chain, so you may want to discuss any follow up chemotherapy after the tumor has been analyzed by a pathologist. Sorry for some bad news, but I am glad you are looking for information. The sooner you address this, the better things will be for Moet. Good luck & thanks for contacting Petco Pet Education Center, formerly Petcoach.

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    Answered By Dr. Dayna, DVM, CVA

    Veterinarian, Certified Veterinary Acupuncturist

    Published on October 12th, 2017

    Unspayed female dogs are very prone to mammay masses. About 50% of these are benign and 50% can be malignant. I would recommend having the mass removed and have her spayed at the same time. Good luck and I hope she does well! Thank you for using Pet Coach.

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    Answered By Mara Howard, DVM

    Veterinarian

    Published on March 26th, 2019

    Thanks for using Petco Pet Education Center, formerly Petcoach! I’m sorry to hear Maxi has a mammary gland mass. Mammary masses in intact dogs can be due to a variety of reasons, including hyperplasia (an overgrowth of mammary tissue), a fatty deposit, or a cancer, among others. Ideally it should be removed and tested to know what it is, so that any treatment she may need could be determined. I would recommend discussing with your regular veterinarian what your options are. Good luck!

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How can you tell if a lump on a female dogs breast is probably cancer over just an infection in the mammary gland without having to go to the vet. I would like to have an idea before hand so I can kind of prepare my elderly grandmother.
Hi, thanks for using Boop by Petco! There is no way to tell if a lump in the mammary gland is cancer or benign with out a fine needle aspirate (which still may not tell you 100%) or removing the mass and biopsying it. Mammary gland infections are rare. The smaller the mass the more likely it’s benign. Spaying a dog before too many heat cycles has proven to protect against mammary cancer in dogs. I wish you the best!
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