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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Breast Cancer Signs in Dogs: What to Look For and How to Think About Mammary Cancer

Updated: May 15th, 2024


Finding a lump on your dog’s breast is not good: Learn how to examine your dog for breast cancer and when to head to the veterinarian.

Breast cancer … in dogs? Can dogs even get breast cancer? Yes, they do.  We don’t call it by the same name; in dogs, we call it mammary cancer. But because the mammary gland is the bulk of the breast, and the disease is very similar, mammary cancer is, in fact, dog breast cancer.

Thankfully, breast cancer in dogs is not as aggressive as breast cancer usually is in humans … but it’s serious, nonetheless. For a full discussion of breast cancer, including its warning signs, treatment, and special diet considerations, please see chapter 31, which starts on page 320 of The Dog Cancer Survival Guide.

Signs of Breast Cancer in Dogs

Signs of breast cancer in dogs include the following:

  • small nodules (bumps) within the mammary tissue that feel like little BBs under your fingers
  • larger nodules within the mammary tissue, still under the skin
  • bloody discharge from the nipple
  • straw-colored discharge from the nipple
  • pus-like discharge from the nipple
  • larger, deeper growths in the mammary tissue that protrude visibly and can be seen as lumps

Want to learn more about mammary tumors and how to treat them? Get the Dog Cancer Survival Guide, and flip to Chapter 31

Spaying and Breast Cancer

Veterinarians often advocate early spay for females because it can prevent breast cancer later on. This is usually done before the first heat comes at about six months.

And it’s true: female dogs who have been surgically sterilized before their first heat, which is usually around 6 months of age, usually live essentially free of breast cancer.

As the spay age increases, this protection drops.

Sounds good, right? Well, yes, as far as breast cancer goes. But you should also know this: early spay and neuter before the first heat is associated with increased risks of other types of cancer.  Those other types include the very aggressive osteosarcoma and transitional cell carcinoma.

This is why we debate whether early spays help avoid cancer. The evidence is mixed. Early spays almost completely eliminate breast cancer, which is nice. But early spays INCREASE the risk of more aggressive cancers.

Found a Lump on Your Dog’s Breast? Get It Checked.

The most critical thing to remember is that if you have a female dog who has a bump in the area around the teat (nipple), please get it checked.

Many of these growths are life-threatening.  And if you have a female dog who is not spayed (intact), or was spayed later in life (at more than 6 months of age), examination of the mammary tissue of your dog may be a lifesaver.

How To Give Your Dog a Home Breast Exam

A breast exam in dogs? Yes, you heard it here first.  You should absolutely examine your dog, especially if she is intact or spayed late.

How do you do it?

First, you have to be able to see and feel her belly. Many dogs already like to lay on their sides or back.  If your dog “gives belly,” you can do her exam then … but even dogs who won’t roll over can still be examined.

Whether giving belly or standing up, here’s what you do.

First, find the mammary glands. Dogs normally have ten, two rows of 5 going down the length of the body, one on the left and one on the right. If your dog has an extra teat or a missing teat, or if they are not perfectly aligned from left to right, don’t worry. Variations are normal!

Second, use your fingers to “see” as well as feel, as instructed below. There are two separate techniques to use — so don’t skip these steps.

  • To make sure your dog is comfortable, try doing this with two hands, one on the left chain and the other on the right chain.
  • Keep your fingers flat and use the pads of your fingertips to “fan” through the mammary tissue up and down the torso, from the head to tail. Start on the first teat on both sides and work down toward the last teat on both sides, feeling for “blips” or bumps under your fingertips.
  • Still keeping your fingers flat, fan your fingers left to right, from the first set of teats to the last. You are still looking for those little blips or bumps.
  • Next, use the second technique, which is to gently press the mammary tissue to look for deeper bumps or lumps. On each teat, gently gather the mammary tissue between your thumb on one side and your index and middle finger on the other. Keep in mind that this could be sensitive tissue, so be gentle! Gently roll the tissue with your thumb as your fingers hold the other side. Move your thumb in a circular motion and feel for blips and bumps between your fingers.
  • Remember, you are looking for little lumps and nodules that feel different from the surrounding mammary glands.
  • Any area that is hard or different is worth having a veterinarian take a look at.
  • If you can see pus, blood, or any other abnormality on the mammary tissue, get it looked at.

How often to do an examination like this on your dog?  I suggest every month or so for female dogs above the age of 7 years.

Even if your dog had an early spay, do a breast exam every once in a while for your own peace of mind. It’s well worth the few minutes.

Treating Breast Cancer in Dogs

Breast cancer in dogs is best treated with a combination of different Full Spectrum steps.  In my patients, I use surgery, dietary changes, Apocaps, deliberate efforts to increase life quality, reduction in body fat (a risk factor for mammary cancer), immune-boosting and anti-metastatic supplements, touch therapies, and more.  As a rule, this cancer does not respond very well to chemotherapy.


Dr D

Spay/neuter and the association with cancer in dogs: part one

Leave a Comment

  1. Stacyschueller on September 11, 2022 at 8:16 pm

    My dog Ben has a red hard lump and it is big as golf ball and loosing his hair on his chest his penis and bills and on his chest and stomach

  2. David wise on October 25, 2020 at 2:02 pm

    My dog has bumps like beebees on her stomach and her vaginal area is all blooded. What should I do??

    • Molly Jacobson on October 26, 2020 at 11:17 am

      Get her to the vet and get her checked out, David — those are not good symptoms. Good luck and warm wishes.

  3. Jerry Bradshaw on October 4, 2020 at 4:25 pm

    Hello : I have a 8 year old German Shepard , she is very gentile , but still barks at leaves falling from our tree , I felt of her belly and she has a Knot under the skin about the size of a mans Thumb ! She is not showing signs of pain , but I live on Social Security and I worry about the cost of this , is something that will cost me my home ? Or is it much less than what Humans go threw with Kemo ? I no you cant give an exact price , but a Range of the price , I want to do all I can for her , she keeps me safe , I owe her that ! Thanks Jerry Bradshaw

  4. Jacqueline on September 22, 2020 at 1:14 am

    My dogs nipple has disappeared and the hole looks to have pus in it.

  5. Nicky Wasserman on September 18, 2020 at 10:58 am

    8 year old whippet bitch who is spayed had a droplet of brownish clear liquid which came from her lower nipple nearest her hind legs the last row, whilst I stroked her belly as she enjoyed her sun bathing.
    Could this be something I need to take seriously ?
    Thank you

    • Molly Jacobson on September 18, 2020 at 11:13 am

      Hi Nicky, please get that checked out by a veterinarian — it is definitely concerning. It’s not necessarily cancer, but it’s not normal. Best of luck to you and your girl!

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