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Can Dogs Get Breast Cancer

Macrodissection Of Tumor Samples And Rna Isolation

Dr. Wendy King on Canine Breast Cancer

Macrodissection was performed on all tumor specimens to ensure high tumor cellularity. Only sections with more than 70% carcinoma cells were included in the study as shown by digital image analysis . For mRNA isolation, tissue sections were transferred into 300 l of lysis buffer and homogenized . RNA was extracted and purified using a commercial system . The RNA quality was controlled using the BioAnalyzer and only high quality RNA was used for microarray analyses. For reverse transcription a commercial kit was used. 100 ng of total RNA of each sample were used for reverse transcription of each tissue sample and the reactions were performed exactly according to the manufacturers instructions. cDNA was stored in low adhesion tubes at -20°C.

Frequency Of Occurrence Of Mammary Tumors According To The Tissue Of Origin

During the study period, the comparison of the frequency of occurrence with their tissue of origin presented certain changes in the biological behavior of mammary tumors . MN of epithelial origin showed the highest number of cases, followed by mixed tumors. During 2006 and 2008, a sustained increase was recorded for the occurrence of epithelial and malignant mixed tumors. BN were mostly represented by mixed-origin mammary lesions, and least frequently by epithelial type. Consistently, both MN and BN lesions were the less frequent. Since 2006, there was a clear decrease in benign mammary lesions , in contrast to the increased number of cases of MN. . The relative frequency of histological types differed between MN and BN . Epithelial tumors occurred in 69% of the malignant lesions, while benign mixed tumors were more plentiful in comparison to MN . The annual frequency of epithelial and mixed tumors was different between benign and MN . Despite the fact that mesenchymal MN showed an annual prevalence four times higher than BN, no significant difference was found . It is important to mention that highly significant differences were found when comparing the average annual frequencies of the three histological types for each biological behavior.

Relative frequency of benign or malignant canine mammary tumors according to the tissue of origin.

Clinical Signs Of Mammary Tumors In Dogs

The last two mammary glands are usually involved more than the other three sets. They often start out feeling like a small, firm nodule, almost like a BB pellet. There can certainly be more than one nodule or mass per gland.

In advanced stages, the masses become larger and may even become an infected, open, draining sore. If malignant, one of the most common areas of the body that they spread to are the lymph nodes.

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Breast Cancer In Dogs

Getty Images/Elen11

Breast cancer is a common concern among humans, but dogs can also develop this disease. While not all mammary tumors in dogs are malignant , the early symptoms of cancer, benign growths, and other mammary conditions look very similar. Lumps in the mammary tract, redness, or nipple discharge should be evaluated by a veterinarian to determine the cause and treatment options.

What Does Breast Cancer Look Like In A Female Dog

Even your pet dog can have breast cancer

The primary sign of breast cancer in dogs is a lump, or lumps, in the mammary glands. Most dogs have between eight and ten nipples and typically develop about five mammary glands, with each teat having 7-16 duct openings . Mammary tumors usually start as tiny lumps but grow rapidly.

The tumors can be felt in or near the nipple, and the size and appearance of the lumps vary according to the type of tumor. Some may appear red, swollen, and inflamed, while other lumps could be hard or soft.

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Canine Mammary Tumors And Metastatic Disease

Depending on the subtype diagnosis, CMT can be fatal due to the development of metastatic disease. Studies have shown that 50% of canine mammary carcinomas metastasise to local lymph nodes. Lymph node involvement invariably leads to distant metastases, which is seen most commonly in the lung, although metastatic bone lesions can also occur . This clinical course is similar to HBC, where ~7% of women will present with metastatic disease and 20% of those with local disease will eventually develop metastatic lesions . Although research has identified several prognostic markers such as age, tumor size, local/distant metastases, clinical stage and histological subtype that can separate human and canine patients into cohorts that have greater recurrence or mortality risk , a detailed understanding of the molecular mechanisms which influence how these cancers metastasise remains unclear.

Table 2. Canine mammary tumor prognostic factors .

Main Morphological Diagnosis In Canine Mammary Tumors

Figs Figs779 show the relative occurrence of a variety of morphological types of CMTs. As mentioned above, mixed BN accounted for the highest number of the total cases, of which 35.9%, 30.9% and 2.4% were benign mixed tumors , complex adenoma and fibroadenoma , respectively. The most frequent benign lesions were tubular adenomas , followed by papillary adenomas , cystic tubular adenomas , papillary cystic adenomas and adenoma. Hemangioma and osteoma represented the benign mesenchymal tumors . From the malignant epithelial tumors group, the most frequent morphological diagnoses corresponded to tubular carcinoma , papillary carcinoma , solid carcinoma , anaplastic carcinoma and cystic papillary carcinoma , among others.

Times series showing the annual frequency allocation of the main morphological types: benign and MN in the epidemiological curves, formed with the 25th, 50th and 75th percentiles for the total frequency of mammary lesions.

The mixed-origin MN were complex carcinoma and carcinosarcoma . Finally, osteosarcoma, sarcoma and hemangiosarcoma were diagnosed within the mesenchymal MN .

Age group distribution. Female dogs diagnosed with benign or malignant neoplasm.

Maltese dogs were mainly associated with epithelial tumors . Medium-sized dogs formed a well-defined group, showing a strong association with mixed-origin tumors and two of the main epithelial tumors .

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Can My Dog Get Breast Cancer

October 27, 2021 at 1:00 PM byNikki Wardle

The short answer is yes, your dog can get breast cancer, better known in canines as mammary cancer. In fact, mammary cancer is the most diagnosed tumor in female dogs that are still intact. Just like with humans, these tumors can metastasize and spread to other areas of a canines body.

What Is A Mammary Tumor

Dogs to detect breast cancer

A mammary tumor develops because of abnormal replication of the cells that make up the breast tissue. Mammary tumors can be benign or malignant . These two forms of the disease have different diagnostics, treatments, management, and prognosis .

There are several different types of malignant mammary tumors, with carcinomas being the most common. Carcinomas arise from epithelial cells, tubules of the mammary glands, or other cells found in the mammary chain.

There are other cancers that can affect mammary glands, including osteosarcomas .

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What Causes This Cancer

The exact causes for the development of mammary tumors in dogs are not fully understood. It is well known that exposure to specific hormones, namely progesterone, increases the risk of developing mammary cancers in dogs. This is because progesterone stimulates growth factors that cause mammary cells to multiply.

“Dogs spayed prior to their first heat have only a 0.5% risk of developing mammary tumor”

The incidence of these tumors is related to whether a dog is intact or has had an ovariohysterectomy . Dogs spayed prior to their first heat have only a 0.5% risk of developing mammary tumor. However, after a first or second heat, this dramatically increases to a risk of 8% and 26%, respectively. Age also appears to play a role the risk of tumor development significantly increases once a dog reaches seven years of age and continues increasing until 11-13 years of age. This increased risk is breed-dependent, indicating that there is a genetic component.

Dog Mammary Cancer Stages

There are five stages of mammary tumors in dogs. The stage of your pets cancer could help determine the right treatment, prognosis, and life expectancy.

The characteristics of each stage follow the tumor size , spread to regional lymph nodes , and distant metastasis .

Details on each stage are listed below:

Stage 1

  • Lymph node spread: Regional spread present
  • Distant metastasis: Distant metastasis present

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Limitations In Current Pre

In the United States of America it is currently estimated that drug development from inception to regulatory approval requires ~13 years and between $1.82.6 billion despite this enormous investment, between 8695% of drugs fail to show efficacy or gain approval for use. The majority of agents fail during clinical trials, after a considerable amount of time and money has already been invested in drug development . The situation is even worse for the development of new cancer drugs, where only 36% of drugs reach clinical use . There are numerous limitations associated with traditional pre-clinical studies which tend to focus on cancer cells grown in 2D or 3D cultures or murine xenograft models to assess the efficacy of cancer agents these limitations have contributed to these high drug attrition rates. One method by which traditional drug development strategies could be improved is to integrate translational pre-clinical animal models into the drug development process at an early stage. These models provide an opportunity to evaluate all aspects of drug development, ranging from efficacy, pharmacokinetics/dynamics and toxicity assessment, through to formulating dosing schedules. These studies could be completed before drugs are taken into more expensive and time-consuming human clinical studies. The early discovery of drug failures would allow drug refinement prior to human clinical studies and ultimately reduce the failure rates observed in these trials .

Causes Of Mammary Gland Tumors In Dogs

Symptoms Of Breast Cancer In Female Dogs : Genetic studies of mammary ...

Mammary tumors are common, especially in unspayed female dogs, as hormones like estrogen and progesterone play a role in both mammary development and cancer formation. The exact cause, however, is unknown at this time.

Mammary tumors are less common in dogs that are spayed. The likelihood of a dog spayed prior to her first heat cycle developing a mammary tumor is about 0%. If that same dog were spayed after her first heat cycle, the chance of mammary tumor development would rise to 8%. If the same dog went through two or more heat cycles, she would have about a 25% chance of developing a mammary tumor.

Even though only about half of these tumors are cancerous, any tumor should be taken seriously and tested for further diagnosis.

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Canine Cancer And Your Dogs Longevity

  • 30% of your dogs longevity, including his or her cancer risk, is due to genetics. This is what your dog inherited from his parents. Unfortunately, we cant do much to alter genetics.
  • 70% of your dogs longevity is attributed to diet and lifestyle. That means if you have a dog with a high cancer risk, there is a 70% chance you can alter the outcome by making simple changes in his nutrition and lifestyle. Thats good news!

Traditionally, statistics for canine mammary cancer tell us that removing your female dogs estrogen source prior to her first heat cycle reduces the odds of getting breast cancer by 99.5%. Therefore, spaying your dog reduces this risk significantly. The risk rises by approximately 8% if she is spayed after her first heat, and by 26% after her second. Note that male dogs and even spayed female dogs can still develop breast cancer. In addition, spaying your female dog prior to her first heat is not a 100% guarantee that she wont end up with cancer. Thats because not all cases of mammary cancer in dogs are hormonally dependent they can develop with or without the presence of estrogen.

What Causes Mammary Tumors

The exact cause for the development of mammary tumors is not known exactly. What is known is that exposure to certain hormones, specifically progesterone which stimulates growth, can cause mammary cells to multiply.

For dogs seven years or older, the risk increases until about the age of 1113.

Mammary tumors usually strike one in four unspayed female dogs over the age of two. 90% of tumors found are benign and mammary cancer is rare. Females spayed before their first cycle reduce their chance of mammary tumor from 25% to .05%. If spayed between their first and second cycle, the risk of mammary cancer is about 8%.

Types of mammary tumors

  • Malignant About 50% of all mammary tumors are malignant. Of those found to be malignant, 50% of those have already spread to other parts of the body when they are initially found.
  • Benign As you may have guessed, the other 50% of mammary tumors found on dogs are benign.
  • Hyperplasia or dysplasia These tumors appear during a heat cycle and will then dissipate once the heat cycle is over.

Breeds that have a greater chance of developing mammary tumors are:

  • Boston Terriers
  • Toy and Miniature Poodles

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Signs Of Breast Cancer In Dogs

Similar to human breast cancer, mammary tumors in dogs can range in size. Breast tumors in dogs often grow quickly with an irregular shape. They can also cause bleeding and ulceration. Even if your dog has a tumor that doesnât exhibit these signs, that does not mean theyâre cancer-free. Small tumors that have been present for a while can suddenly grow aggressively. As with most other types of cancer, once malignant tumors in dogs start to grow, the cancerous cells can spread to other parts of the body.

Symptoms to look for are:

  • Growing lumps or sores that donât heal

  • Drastic changes in a dogâs appetite or weight

  • Offensive odors

  • Persistent lameness or stiffness

  • Difficulty breathing, urinating, or defecating

If you find a lump on your dog, do not wait to go to the veterinarian. Itâs always best to play it safe and have them examined by a professional. Even though half of all mammary tumors in dogs are benign, thereâs no point in playing guessing games when it comes to your dogâs health.

Understanding Breast Cancer In Dogs

Woman believes dog detected breast cancer

Like all female mammals, dogs have breasts to feed their young. But unless you have had a pregnant dog, its easy to forget because dogs do not have pronounced breasts the way that humans do except when they are pregnant or nursing. The word breast is just another name for the mammary gland where breast cancer occurs.

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How To Prevent Breast Cancer In Dogs

The best way to prevent breast cancer from developing in your dog is to get her spayed when your veterinarian recommends doing so. Spaying helps to substantially decrease the likelihood of your dog developing breast cancer.

  • Kim HW, Lim HY, Shin JI, Seung BJ, Ju JH, Sur JH. Breed- and age-related differences in canine mammary tumors. Can J Vet Res. 2016 80:146-155.

  • What Are The Causes Of Breast Cancer In Dogs

    Mammary tumors are the most common cancer developed in female dogs . Despite its prevalence, the causes of breast cancer in dogs are not thoroughly understood. However, there is some evidence that exposure to increased progesterone levels could cause cancer development .

    Progesterone stimulates the secretion of growth hormonetumors develop due to cancer cells dividing and growing uncontrollably . The increased levels of growth hormone could cause these rapidly multiplying cells to do so even faster, leading to the development of mammary cancer.

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    Signs Of Tumors In Dogs

    If your pooch isnt feeling welllike eating less, lethargic, or losing weight, that might be a sign of cancer, among a myriad of other possible ailments.

    The most common clinical sign of mammary cancer is one or more palpable masses underneath the skin by any one of the breast areas. These masses range in size but are firm and take on a round-like shape. In some cases, the skin over these masses will break open and could bleed. In other cases, discharge could develop from the mammary glands.

    If you notice any newly developed lumps on your dog, get them into your vets office sooner than later. They will need to do a biopsy in order to determine if they are benign or malignant.

    Types Of Mammary Tumors

    How Spaying/Neutering Helps Prevent Cancer in Pets

    The diagnostic process of possible mammary cancer can identify the type of tumor your pet has. Some of the most well-known include:

    • Inflammatory carcinoma: This is the most malignant type and could rapidly spread throughout the dogs body.
    • Adenocarcinoma: One of the most common types of tumors
    • Fibroadenoma: A type of benign tumor that is typically painless
    • Mixed mammary tumor: The most frequently occurring tumor in dogs

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    About Half Of The Tumors Are Malignant

    Breast cancer is an omnipresent topic in human medicine these days, but what about our canine companions? The risk is even higher for female dogs than it is for women. Mammary tumors in female dogs account for 42% of all diagnosed tumors, with a lifetime risk of 23-34%, according to the Veterinary Society of Surgical Oncology . Compare that to women, who have a 12.4% lifetime risk according to Susan G. Komen, an American breast cancer organization. Its sobering.

    At a cellular level, mammary tumors in dogs and cats are very similar to human breast cancer tumors, says Dr. Scott Coonrod, the Judy Wilpon Professor of Cancer Biology and director of the Baker Institute for Animal Health. And they may occur in pets even more often than they do in humans.

    Thats because intact female dogs have fully-developed mammary tissue. A dog spayed prior to sexual maturity is at a reduced risk of mammary cancer because the spay removes the ovaries, which produce the estrogen that is significant to the full development of the mammary glands.

    According to the American College of Veterinary Surgeons, the risk of your dog getting mammary cancer is:

    • 0.5% risk for female dogs spayed before their first heat cycle
    • 8% risk for female dogs spayed after their first heat
    • 26% risk for female dogs spayed after their second heat
    • Additionally, 50% of mammary tumors are malignant

    Obesity, especially at a young age, as well as breed, may also influence the risk.


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