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Mammary Tumors In Dogs (Breast Cancer): Symptoms, Treatment & More


Last Updated: April 3, 2023 | 6 min read | Leave a Comment

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Person pointing to a mammary gland on a dog's belly

Cancer in dogs is, unfortunately, common, particularly as they age. Our canine friends are living longer, and advances in veterinary care mean that cancers are now diagnosed more frequently. Mammary tumors are a form of cancer that affects the mammary, or breast, tissue in dogs. They are more common in female than male dogs. Early detection may allow for more treatment options and a better prognosis. Let’s find out more about breast cancer in dogs, the signs of breast cancer in dogs, treatment options, and outcomes.

Can Dogs Get Breast Cancer?

Mammary tumors in dogs appear as lumps of varying shapes and sizes in the mammary glands. The mammary glands are the tissue that surrounds your dog’s nipples on the underside of its chest and belly. Breast cancer, or mammary cancer, is much more common in female dogs than in male dogs.

Intact (un-spayed) female dogs are at greater risk of developing mammary cancer than neutered (spayed) dogs. This is because neutering (spaying) removes the ovaries, which are responsible for producing the hormone estrogen. Oestrogen stimulates the development of mammary tissue. Therefore neutering bitches when they are young reduces the development of mammary tissue. On average, one in every four unneutered female dogs is affected by breast cancer.  

Breast Cancer In Dogs Symptoms

Dogs have five pairs of mammary glands, starting near the armpits underneath the front legs and extending to the groin. Tumors are normally found by pet owners who find a lump in one or more of these glands. The mass may be normal color, red or purple, soft, hard, and in some cases ulcerated. Other symptoms include swollen glands, changes to the nipple, discharge from one or more glands, or changes to the skin overlying the mammary glands.

Causes Of Breast Cancer In Dogs

The causes of breast cancer in dogs are not well understood, and there are likely to be many factors that contribute to the development of this disease. Breast cancer in dogs has a hormonal component as spaying your female dog before their first season, or when they are young, massively decreases their chance of developing this type of cancer.

Genetics also plays a factor as certain dog breeds seem to be predisposed to developing breast cancer, including Spaniels, Dachshunds, English setters, German Shepherds, Fox Terriers, Poodles, and Pointers.

Types Of Mammary Tumors In Dogs

The language surrounding cancer can be confusing, and definitions are difficult. Tumors (also called growths) can be cancerous (malignant) or non-cancerous (benign), depending on how they behave in the body. 

  • Benign tumors are not invasive, do not spread to other areas of the body, and are easier to remove surgically.
  • Malignant tumors can invade surrounding tissue and spread to other areas of the body, causing damage to organs.

Distinguishing between benign and malignant tumors requires special knowledge and laboratory equipment. Tumors result from the uncontrolled growth of cells in the body. Tumors are named after the type of cells that have overgrown.

The most common type of mammary cancer in dogs is known as mammary carcinomas (malignant) or mammary adenomas (benign). Inflammatory mammary carcinoma is a highly malignant type of mammary tumor but comprises less than 5% of all mammary tumors. Other types of tumors can also occur in the mammary glands or nearby, including lipomas, sarcomas, and mast cell tumors.

The ‘grade’ of a tumor helps describe how aggressive the tumor is and how likely it is to spread elsewhere in the body. Grading of a tumor takes place on tissue samples taken from a biopsy or after surgical removal of the tumor.

How Is Breast Cancer Diagnosed In Dogs?

A veterinary surgeon will examine the mammary glands of a dog by palpating them for masses, growths, or skin changes such as ulcers or infections. Your vet will check any lumps to determine their size, shape, consistency, and mobility. Approximately 50% of all mammary tumors are malignant, and 50% are benign.

However, it is not possible to determine this from examination alone. A biopsy of the tumor is the only test that can differentiate which type of tumor is present. Biopsies are surgical procedures that are performed before or at the same time as the surgical removal of the mammary tumor. Veterinary surgeons may also take samples of lymph nodes (glands) that drain the area and perform other diagnostic tests such as ultrasound scans and x-rays to look for evidence of the spread (metastasis) of cancer.

Treatment Of Mammary Masses In Dogs

Surgery is the main form of treatment for mammary tumors in dogs. Generally, one or more mammary glands are removed. If a tumor is found in multiple mammary glands, removal of the entire mammary chain (all 5 glands on one side of the body) may be recommended. Following surgery, the tissue removed will be analyzed by a pathologist to help diagnose the type of tumor and the grade.

Early-stage mammary tumors in dogs may not require any further treatment, but regular check-ups with a vet will be required to monitor for the recurrence of breast cancer.

Later-stage or high-grade mammary tumors that are at risk of spreading may benefit from chemotherapy following surgery. Chemotherapy drugs are drugs specifically designed to kill or slow down the growth of cancer cells. There are lots of different types of chemotherapy protocols used to manage breast cancer in dogs that, include oral (tablet) drugs and injectable medication.

Unfortunately, some dogs with multiple tumors, or very large tumors, may not be suitable for surgery as cancer may be too advanced or already have spread to other areas of the body.

Dog Breast Cancer Surgery Cost

The cost of treating breast cancer in dogs varies depending on the type, severity, and location of the tumor. Diagnostic tests such as blood tests, x-rays, and scans will contribute to the overall cost of treatment. Surgical costs depend on the size of the mass and the complexity of the surgery required.

It can range from $500 for a simple surgery to over $5000 for a more complex surgery. If your dog requires a period of time in the hospital following surgery, or consultation with a specialist, such as an oncologist, then costs can increase.

Having pet insurance before a dog is diagnosed with conditions like cancer can save you thousands of dollars in vet bills. Learn more about if pet insurance covers cancer and how it can help you financially.

Home Remedies For Dog Breast Cancer

There are no treatments that can be given at home to get rid of breast cancer in dogs. Surgical removal of mammary masses is the recommended treatment. Regular examination of your dog’s mammary glands by feeling for lumps or bumps is the best thing you can do at home to detect breast cancer in dogs. Early detection often means more successful treatment, as surgical removal of mammary tumors can be curative. Therefore, if you notice changes to your dog’s mammary glands or detect a lump or mass, don’t delay in seeking veterinary advice.

Evidence suggests that neutering (spaying) your dog, especially when they are young, significantly reduces the risk of breast cancer. Neutering your dog is the best preventative method you can employ to reduce its risk of developing mammary tumors.

Following surgery, your vet will talk through how to look after your dog at home. Home care will involve monitoring the surgical wound for swelling and discharge, ensuring your dog cannot lick or interfere with the wound (sometimes by using a medical pet shirt or Elizabethan collar), and restricting their exercise until they have healed from surgery. If your dog has medications to take at home, ensure you know exactly how and when to give these medications and what side effects to look out for.  

Mammary Tumors In Dogs Life Expectancy

Dog breast cancer survival rate depends on the type and severity of the tumor. The prognosis for dogs with benign tumors is excellent, and surgery is often curative. Around 50% of dogs with malignant mammary tumors also have a very good prognosis following surgical removal. The remaining 50% are at risk of the tumor spreading. This can cause disease associated with other organs (such as the lungs, stomach, and liver), and survival times are usually less than one year.

Dogs with inflammatory mammary carcinoma have a very poor prognosis, and their survival time is only weeks to months. Thankfully, this type of breast cancer in dogs is rare. 

The prognosis for your dog’s recovery depends on many factors and is unique to your dog. The size of the tumor, the histologic grade, lymph node involvement, and risk of metastasis are the most important prognostic indicators. Early detection of tumors is key for long-term survival. 

Caring For Your Canine’s Cancer

Naturally, we want the best for our canine friends, and discovering they have breast cancer can be a frightening time. If you are concerned your dog may have breast cancer, don’t delay in seeking veterinary care, as early intervention could save their life. Your veterinarian will help guide you through treatment options depending on the cancer type and stage so that you can make the best decision for your dog. Learn about other cancers in dogs, including bone, skin, and lung cancer.

The information provided through this website should not be used to diagnose or treat a health problem or disease; it is not intended to offer any legal opinion or advice or a substitute for professional safety advice or professional care. Please consult your health care provider, attorney, or product manual for professional advice. Products and services reviewed are provided by third parties; we are not responsible in any way for them, nor do we guarantee their functionality, utility, safety, or reliability. Our content is for educational purposes only.

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