Breast Cancer in Dogs: Diagnosis, Management, And Support

Breast cancer dogs
Wyatt Robinson
Written by Wyatt Robinson

Dogs can give several years of happiness to the pet parent. It is something that can be fulfilling and worthwhile at the same time. Moments of playtime, or just a simple afternoon sitting on the couch while watching your favorite football game. Then suddenly as you brush your dog’s underside, you felt something unusual to the touch. A lump. You immediately thought that it could be something serious, so you secured an appointment with the dog’s veterinarian, she ordered to have some tests taken, and a specimen was sent to the laboratory for further testing.

Few days later, you have received the devastating news. Results reveal that it really is cancer, and the veterinarian would like to discuss the treatment options to address the illness. Nonetheless, where should you start? How did it happen? It is understandable that breast cancer is one of the most sensitive kinds of illnesses that disturb the lives of both dogs and humans that is why it is important to know the basics of breast cancer in dogs. A disease that is fatal, but is also highly preventable. To ensure that that lump you feel is really cancer, you should first check out this article on bumps and lumps on dogs.

Types of breast cancer in dogs

Breast cancer in dogs is one of the most common cancer types that affect a significant amount of dog population all over the world. There are several types of breast or mammary cancers in dogs. About half of all tumors that occur in the breast are considered benign. Unfortunately, the other half is considered malignant. The gold standard in identifying whether a tumor is benign or malignant is by performing a biopsy and histopathology to determine the treatment management for the confirmed cancer diagnosis.

It has been considered that the most common kind of benign tumor is actually a combination of several different cells. For a tumor to have more than one type of cancer cell is actually rare. The combined tumor is called a benign mixed mammary tumor and is made of connective and glandular tissue. Other benign tumors include:

  • Duct Papilloma
  • Simple Adenomas
  • Complex Adenomas
  • Fibroadenomas

It is considered that the most common type of benign canine breast tumors is actually a combination of several different types of cells. For a single tumor to have more than one type of cancerous cell is actually considered rare in many species. This combination type of cancer in dogs is called a benign mixed breast tumor and contains both connective and glandular tissue.

On the other hand, malignant breast tumors include:

  • Solid Carcinomas
  • Osteosarcomas
  • Fibrosarcomas
  • Malignant Mixed Tumors
  • Papillary Adenocarcinomas
  • Tubular Adenocarcinomas
  • Anaplastic Carcinomas
  • Papillary Cystic Adenocarcinomas

There are certain breeds that have an increased risk based on their genetic predisposition. Gender is definitely a given, although male dogs are not exempted in having this type of cancer. These are the breads that are more at risk:

  • Pointer
  • Boston Terrier
  • Cocker Spaniel
  • Poodle
  • English Setter
  • Lhasa Apso
  • Brittany Spaniel
  • Fox Terrier

There are breeds that are prone to breast injuries because of their anatomical structure, such as the Dachshund and Basset Hound. These mammary cells may be irritated, bruised or become ulcerated, and may only require supportive treatment that will help the wounds heal. If the wound, however, appears a bit different compared to other typical-looking wounds, it will be best to have the wound checked by the veterinarian as well.

Symptoms of breast cancer in dogs

Mammary tumors can be observed as either a solid mass or with multiple swellings. When the tumors grow in the mammary tissue, these tumors can be detected by palpating the mammary glands. Tumors feel like small nodules or peas under the skin. They are more obvious to the touch because they are hard and immobile.

These tumors can grow at a very fast rate, up to double their original size in a matter of months. Malignant tumors are more aggressive in terms of growth, and they are irregular and are attached to the underlying tissues. There are instances that cancerous tumors bleed and ulcerate. However, there are malignant tumors that retain their small size for a long time then suddenly grow at an alarming rate.

Identifying a tumor based on physical appearance is a very difficult task because there are tumors that look similar but they are different in action and the treatment regimen will be different as well.

Scan in prgress

A biopsy or even a total tumor removal and analysis are very important to identify the tumor if it is benign or malignant, and if it already spread to the surrounding structures like the lymph nodes and the lungs. Supporting diagnostic procedures such as chest x-ray will also augment the resources in providing an accurate diagnosis. Breast cancer can spread to the other parts of the body when the cancer cells break free from the tumors and go into the lymphatic system.

Dogs have regional lymph nodes called the axillary and inguinal lymph nodes. Basically, the spread of cancer that involves the axillary nodes move upward, while the cancer cells that spread through the inguinal regions reach the kidneys, liver, and even the lungs.

Treatment for breast cancer in dogs

The treatment options for breast cancer will directly depend on the type of cancer, and the extent of the disease into the dog’s body. There are three managements that are usually implemented either independently or collaboratively: Surgery, Chemotherapy, and Radiation Therapy.


Once the mass has been identified, surgical removal will be performed unless the dog is already in advanced age and it can no longer endure the procedure. If a surgery is done at the earliest possible time, the cancer can be totally cleared in more than half of the cases of malignant cancer. The surgery procedure will completely depend on the veterinarian’s discretion.

There are cases that only the mass is removed, while there are other cases that require the mass and the surrounding structure such as lymph nodes and mammary tissue to be excised as well to inhibit the spread of the disease.

Dog on surgery

Aside from old age, there are still some tumor types that surgery will be a very difficult choice. Sarcomas, for example, make the removal very difficult and even if the tumor has been removed successfully, it has a high chance of tumor regrowth from the removed area, which can aggravate the situation instead of improving it. Pet parents might be confused that the surgery for breast cancer in dogs will be similar to that of humans. As dogs have a more complex mammary network compared to humans.

However, the anatomical structure of dogs have all of the involved breast tissue and lymphatic system to be located outside the muscle layer unlike in human structure where it is a combination of muscle, fat, and skin layers.

The surgery in dogs is easier and recovers faster when compared to human standards. This is the kind of surgery that is considered as major based on veterinary standards, but recovery period can be as short as two weeks or less, and the dog can resume its normal routine after that. Some veterinarians will also perform spaying the patient that will be having the procedure.

Chemotherapy and radiation therapy

Chemotherapy is not as widely received in dogs as it is in humans. However, with the advancing technology and the constant research in improving canine medication and therapeutic approach, this treatment procedure has been gaining attention and implementation by veterinary oncologists. It will be under careful consideration to take this route, together with radiation therapy because this gives a systemic effect.

While it can effectively destroy the remaining cancer cells, it can also damage the healthy cells in the process. It will require significant nutritional and emotional support while the patient is undergoing either chemotherapy or radiation therapy.

Radiation therapy

Radiation therapy can be recommended by the veterinarian in combination with surgery and/or chemotherapy to deliver lasting control or total elimination of a tumor. Radiation therapy is administered to tumors that have not spread metastasized to other parts of the body, and can possibly act as a possible treatment for some confined tumors.

In some cases, radiation therapy can be used for palliation to relieve the signs of the disease. In cases wherein the tumor cannot be totally destroyed, radiation therapy can at least reduce tumor size and can improve the quality of life of the sick dog by reducing pain, bleeding, or internal pressure.

Severe adverse effects in radiation therapy is quite rate, and occurs less than ten percent of the total population of all the animals treated using this approach. However, like chemotherapy, it also damages or kills normal and healthy cells. The adverse effects can be either acute or chronic. The effects that are classified as acute often occur shortly after administration of the radiation, chronic effects are the signs that occur at a later period of time.

The most common adverse effects of chemotherapy and radiation therapy include the following:

  • Decreased Appetite
  • Vomiting
  • Diarrhea
  • Decrease in White Blood Cell Count
  • Hair Loss

These side effects may present themselves in varying levels of severity depending on the frequency and dosage of the administered chemotherapy medication. In hair loss, there are breeds that are more susceptible to hair loss as the primary complication of chemotherapy. It is also noted that there are cancer patients that are more prone to experience diarrhea compared to other breeds.

If you’re looking for a more natural option, you may want to read on the C-Support Herbal Remedy for dogs with cancer.

Prevention of breast cancer

Despite its high incidence, breast cancer, is actually one of the few types of canine cancer that can be prevented easily. Previous research confirmed that there is a connection between spaying of dogs and the reduction of breast cancer incidence. Spaying is considered the most effective preventive measure because a large number of mammary tumors are estrogen receptors, and by removing the primary source of the hormone that will “feed” the tumor.

  • Dogs that have been spayed before it reaches its first heat are placed in an extremely small risk to develop breast cancer. Few cancers are as easily preventable as breast cancer in dogs. There is a direct link between the spaying at a much younger age for female dogs, and the reduction in the incidence in breast cancer.
  • Dogs that have been spayed after their first heat, but before they reach three years old are more at risk to develop breast cancer.
  • Dogs that have been spayed after it reached its third year gains the biggest risk of developing breast cancer. However, the increased risk is still not as significant as dogs that have never been spayed.

The benefits of spaying female dogs at an early age cannot be understated. However, due to lack of knowledge and the indecisiveness of the pet parent, veterinarians still deal with the case on a regular basis.

Preventive early spaying is one of the best procedures that pet parents can do to enhance the overall health and well-being of the dog, reducing the risks of potential health hazards that can develop as the dog’s life progresses. Female dogs that have been spayed before their first heat can develop mammary cancer in an extremely rare possibility, with values as low as 0.05%. This value increases significantly by 8% for the female dog that was spayed after her first heat, and a considerable value of 26% for the dogs that have been spayed after the second heat.

Emotional support for the dog

Unlike humans, dogs can only express their pain and suffering by actions. They cannot express themselves freely, and will completely depend on their pet parents during the entire treatment process. This is extremely important especially if the sick dog was diagnosed with a more advanced, or even terminal breast cancer. The pet parent should have enough patience, and a bit tougher heart to help the sick dog in its journey to recovery.

In earlier stages, it is important that the well-being of the dog and its pet parent should not be compromised. The owner should be able to live a normal life while the treatment is ongoing. That way, he or she could still function well despite the roadblock that can be an emotional burden that can hinder him to live normally especially if the sick dog is something the owner considers as a best friend or his own child. As a stressful situation, it is alright to air out your concerns to your veterinarian as he is the individual that completely understands the situation.

You can also seek the support of your family members and relatives to unload some of your emotional burden. Depending on the location, there are support groups available at the neighborhood or the city for pet parents that have experienced similar cases. In fact, there are foundations that support the continuing research for canine breast cancer.

For pet parents that take care of more than a single dog, the well-being of the other pets should not be compromised as well. Always do your best not to allow them to miss their meals, and make sure they are properly hydrated to prevent any nutritional deficit that can lead to problems in the future.

Breast cancer

In the more advanced stages, the ordeal is mutually unbearable for both the pet parent and the dog. The pet parent will be prepared by the veterinarian for end-stage treatment, and even cessation of life. This is a very difficult situation to be into, and it should be discussed and decided carefully. There are types of cancer that may respond to treatment, even the advanced stages.

However, some types like osteosarcoma respond poorly to treatment and are some of the most painful varieties of cancers in dogs. Your veterinarian will be asking you questions to help you decide without being clouded by emotions because once it has been decided, it cannot be reversed.

It is one of the most uncomfortable topics that any pet parent can experience that is why it is very rarely to hear many discussions both in local communities and online forums. This is due to a decision that may leave the pet parent regretful, if not empty due to the loss of life of a friend that suffered in life.

Prevention, prevention and prevention!

Breast cancer is a very common cancer and can often be treated with high success rate, if detected early. If only all non-breeding dogs and cats were spayed before they reach their first heat, this disease could be eliminated. If you find a growth or lump in the breast tissue of your dog, you should inform your veterinarian right away and not take a «maybe later» attitude.

Prevention and vigilance in notifying the veterinarian for any changes or appearance of a lump that was not there before, can save the dog’s life, and provide you the peace of mind. It will also save you from an emotional ordeal that this illness can bring if detected at a much later stage. As dogs cannot express themselves to you that they want to be tested for any kind of medical condition, the initiative should come from you as a responsible pet parent.

About the author
Wyatt Robinson
Wyatt Robinson

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.