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Mammary Cancer in Dogs

Mammary Cancer in Dogs

Breast Cancer, Mammary Gland Tumor, MGT

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Updated on October 31, 2024
SUMMARY OF CONTENT
Mammary (breast) cancer is the most common cause of tumors in female dogs that have not been spayed.
SEVERITY:
Severity is moderate to severe
  • Diagnosis Icon
    Requires a diagnosis by a veterinarian
  • Time to Cure
    May resolve within weeks after surgery if caught early
  • Treatment Icon
    May be treatable by a veterinarian
  • Prevention Icon
    Spaying female dogs before their first heat cycle reduces the risk of mammary cancer to less then 1%, however, spaying prior to their second heat cycle still greatly reduces their risk of developing mammary cancer compared to those spayed later.
  • Spread Icon
    Transmission is not possible between animals and not possible between animals and people
  • Lab Icon
    Diagnosis requires physical exam, fine needle aspirate and cytology, x-rays
VERY COMMON IN
Common in older, intact (unspayed) female dogs. Some breeds such as chihuahuas, poodles, boxers and Doberman pinchers do see an increased occurrence of mammary cancer.

Symptoms & Signs

Mammary tumors are observed as a solid mass or as multiple swellings underneath the belly. When tumors do arise in the mammary tissue, they are usually easy to detect by gently palpating the mammary glands. When tumors first appear, they may feel like small pieces of pea gravel just under the skin. They can grow rapidly in a short period of time and may double their size every month or so. The dog normally has five pairs of mammary glands. Although mammary cancer can occur in any of the glands, it is more common in the 4th and 5th glands (closest to the hind limbs). The only way to confirm if a tumor is malignant or benign is through diagnostics done by your veterinarian. The risk of malignant mammary tumors in dogs spayed prior to their first heat cycle is a miniscule 0.05%. The risk increases to 8% for dogs spayed after one heat cycle and jumps to 26% in dogs spayed after their second heat cycle.

Diagnosis

It is very difficult to determine the type of tumor based on physical inspection. A biopsy or removal for histopathology is almost always needed to determine if the tumor is benign or malignant and to identify the type of tumor. Aggressive tumors may metastasize to the surrounding lymph nodes or to the lungs. A chest x-ray and physical inspection of the lymph nodes will help to determine if the tumor has already spread. Bloodwork and urinalysis as well as an abdominal ultrasound may also be recommended by your veterinarian.

Causation

Mammary tumors can be small, single nodules or large, aggressive, metastatic growths. With early detection and prompt treatment, many tumors can be successfully treated by your veterinarian. There are multiple types of mammary cancers in dogs. Approximately half of the mammary tumors in dogs are benign and the other half are malignant. The most common benign form of canine mammary tumors is actually a mixture of several different types of cells. This combination tumor in the dog is called a 'benign mixed mammary tumor' and contains glandular and connective tissue. Other benign tumors include complex adenomas, fibroadenomas, duct papillomas and simple adenomas.

Malignant mammary tumors include tubular adenocarcinomas, papillary adenocarcinomas, papillary cystic adenocarcinomas, solid carcinomas, anaplastic carcinomas, osteosarcomas, fibrosarcomas and malignant mixed tumors. Malignant mammary cancer can spread to the rest of the body through the release of individual cancer cells from the various tumors into the lymphatic system. The lymphatic system includes lymph vessels and lymph nodes. There are regional lymph nodes on both the right and left sides of the body under the front and rear legs. They are called the 'axillary' and 'inguinal' lymph nodes, respectively. New tumors may then form at these sites and then release more cells that go to other organs such as the lungs, liver or kidneys.

Treatments

icon AT-HOME CARE
Administer medications as prescribed by your veterinarian.
icon MEDICATIONS
Pain medication may be prescribed after surgery or radiation to aid in comfort of your pet. Examples of pain medications your veterinarian may prescribe include tramadol, gabapentin and Rimadyl. While many medications are often administered for ‘off-label’ or 'extra-label' use in veterinary medicine, it is important to know that off- or extra- label use of a medication can only be done by a veterinarian when there are no other more appropriate medications for a particular pet's circumstances. Your veterinarian must also know all vitamins, supplements, medications etc. your pet is taking to help avoid complications. You must also be sure to follow all instructions provided by your vet carefully and consult your veterinarian with any questions or concerns if they arise.
icon MEDICAL PROCEDURES
The effectiveness of radiation therapy for mammary tumors in dogs has not been thoroughly researched and chemotherapy is typically reserved for advanced cases. Some anti-hormonal drug regimens are being tested in dogs. At this point in time, surgical removal of the tumors is typically the treatment of choice by most veterinarians.
icon SURGERY
Upon finding any mass within the mammary gland of a dog, surgical removal is typically recommended. If surgery is done early in the course of this disease, the cancer can be totally eliminated in over 50% of the cases with a malignant form of cancer. Sometimes a veterinarian may recommend that only the mass itself will be removed. Other times, taking into consideration how the cancer spreads, the mass and the rest of the mammary tissue and lymph nodes that drain the gland will be removed. With some types of tumors, especially sarcomas, complete removal is very difficult and many of these cases will have tumor regrowth at the site of the previously removed tumor. Your veterinarian will determine which option is best for your pet considering the type of growth and overall health of your dog.
icon SPECIALISTS
Most cases of mammary cancer will be referred to a specialist in veterinary oncology or surgery.

Cost Of Treatment

The cost of veterinary expenses varies widely for a variety of reasons, however, surgery to remove tumors may cost as much as $5000 or more depending on the size of the patient, health status and size of the tumor(s).

Recovery

Mammary cancer is a very common cancer, especially in female dogs that were spayed at maturity, and can often be successfully treated, if caught early.

Monitoring

Follow-up exams may be necessary depending on the type of tumor and the type of surgery undertaken. Your veterinarian will likely prescribe a surgical cone and exercise restrictions while your dog recovers from surgery to reduce the risk of injury to the incision site.

Prevention

Spaying female dogs before their second heat cycle greatly reduces their risk of developing mammary cancer. Regular physical exams may catch tumors while they are still very small.

Questions about Mammary Cancer

My dog I heated uses tampon is it an emergency

Unfortunately I'm having a little trouble understand your question as I'm not sure what you mean by "My dog I heated uses tampons..." I'm wondering if Bella ate a tampon or if you wanted to use one on her while she is in heat. I will answer both to be safe. If she ate a tampon, then yes this is a medical emergency and she has to see a vet now. Tampons can easily cause obstructions in the GI tract, especially since they are absorbent and can get large in the stomach from liquid in there. if Bella ate a tampon, you need to take her into a vet immediately to get it removed. If she is on heat, no you cannot use a tampon to control her bleeding. It's not safe to use at all, and are not meant for dogs. You can put a diaper on her to catch any bloody discharge. There are dog specific diapers online and at pets stores, or you can use one made of a human child. Just cut a hole in it for her tail. Hopefully this answers your question. If it doesn't, I'm sorry and ask you post again in the forum for free to it can get answered!

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My senior cat has metastized cancer.17 yrs old. My vet gave her predizone1 and one half tabs a day.i wanted to know if i can just stop the meds.

Is there a reason you want to stop the prednisone? I would recommend not stopping it and if you feel it is better to stop the prednisone then I would recommend weaning off of the prednisone. I would discuss how to wean the prednisone with your veterinarian. Thank you for using Boop by Petco.

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My dog has an ear infection

Sorry to hear Marley isn't doing so well with his ears. It is not possible to tell from tge picture tve exact nature of the irritation but if it is indeed infected (typically red, hot, painful and smelly), he will need prescription medication from his regular vet. In the meantime I recommend gently cleaning tge outer war with cotton wool and a pet safe ear cleaner to reduce the build up of wax/discharge

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My dog vomited a pinkish colour. Does this look like blood vomit? She doesn’t have diarrhoea or anything else. Yesterday i fed her plain chicken with rice.

That is very red vomit, however, this color could be linked to a number of things including blood in the vomit, inflammation of the GI tract, having chewed on a toy this color, eaten a food item this color, or gotten into a plant or other item this color. If the vomiting continues, worsens, or other symptoms appear such as a painful or bloated abdomen, diarrhea or blood in the stool, or severe distress, I would schedule a veterinary appointment right away to rule out more severe issues. In the meantime I would continue the bland diet for 24 hours, and monitor for any additional vomiting or illness symptoms.

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My dog developed a red hairless bloody mass on her skull overnight. I don’t think she bumped her head on anything.

Poor Marley! Unfortunately there are a number of possible reasons for these raised nodules and a picture cannot diagnose the underlying cause. Itis not possible to distinguish between a wound from a bug bite, cyst, benign histiocytoma or even a tumour without a physical exam and possible testing by an aspirate taken by a needle during the exam or even removal and biopsy. I recommend you follow up with your regular vet, especially if it increases in size, is painful or persists.

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Hi my 5 year old dog has this on her nose ( saw it 4 days ago) and getting bigger. What could it be and is there anything I can do? Thank you.

Ouch! Any new or suddenly growing growth like this should be checked out by your vet in person ASAP. Allergies, infections, skin irritation from rubbing it on things, and some growths and tumors can all cause spots like that on the nose, and can also cause rapid changes and discoloration like this. Until you can get to your vet, I would place an Elizabethan (cone) collar on Amber and keep the spot clean and dry to help reduce any further irritation. It is also a good idea to monitor the size and shape of it and how rapidly it is changing as this can help your vet figure out what may be going on. Your vet will likely take a full history as well as a potential sample of the spot to see what cells are present and provide treatment as needed.

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Disclaimer

The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.