A watercolor painting of a dog prone to cancer sleeping on a couch.

What is Cancer in Dogs?

What is it?

Cancer in dogs, much like in humans, is a disease characterized by uncontrolled growth and spread of abnormal cells in the body. It can affect any part of a dog’s body, including organs, bones, and tissues. The causes of cancer in dogs are genetics and environmental factors and are thought to play a role.

How is it Treated?

Treatment for cancer in dogs depends on the type and stage of the disease, as well as the dog’s overall health. Common treatment options include surgery, chemotherapy, radiation therapy, and immunotherapy. The goal of treatment is to remove or reduce the cancerous cells while minimizing harm to healthy cells and improving the dog’s quality of life.

Breed Predispositions

Golden Retriever Boxer Rottweiler Bernese Mountain Dog Great Dane Labrador Retriever Bulldog Beagle Bichon Frise Cocker Spaniel


When Laura noticed a small lump on her cherished Golden Retriever, Charlie, she initially thought it was just a harmless bug bite or skin irritation. As weeks passed, however, the lump grew larger and more worrisome. Filled with concern, Laura took Charlie to the veterinarian for a thorough examination. She was devastated when the vet delivered the news that Charlie had cancer, a diagnosis she hadn’t expected.

Cancer in dogs, like humans, refers to the uncontrolled growth of cells that eventually forms tumors or spread throughout the body. Often extremely aggressive, these abnormal cells in a dog’s body don’t function like the dog’s normal cells. They can grow uncontrollably, invade surrounding tissues, and spread to other areas of the body, such as the lungs, causing damage to the dog’s health, hence posing a significant risk of cancer.

Cancer can affect virtually any part of the dog’s body, including the skin, leading to skin cancer. Different types of cancer, such as lung cancer, can behave very differently in a dog’s body. For instance, some grow slowly and may stay in one spot without spreading for years, while others grow rapidly and spread quickly to other organs.

Various types of cancer can develop in dogs, much like they can in humans. The most common types found in dogs include lymphoma, mast cell tumors, melanoma, and bone cancer. Each type of cancer affects the body differently, and the severity and prognosis can vary greatly depending on the type of cancer a dog has and the stage at which it is identified.

Cancer is a significant health problem, especially in certain breeds like the Irish Wolfhound. It is often the cause of death in older dogs, but it can occur in dogs of any age. However, many forms of cancer can be successfully treated or managed to provide the dog with a good quality of life. The specific outcome for a dog with cancer can depend on many factors, including the type and extent of the cancer and the treatment chosen.

Types Of Cancer In Dogs


This type of cancer affects the lymph nodes and the immune system. It is a very common cancer in dogs and can be seen in any breed, though it is more prevalent in certain breeds. Lymphoma can manifest in various forms, and its effects on a dog can range from mild discomfort to severe illness. It accounts for approximately 25% of all canine cancer cases.


Hemangiosarcoma is a cancer of the blood vessels. It often affects the heart or the spleen, leading to serious complications such as internal bleeding. This form of cancer is common in large-breed dogs and is typically aggressive with a poor prognosis.

Mast Cell Tumors

These are cancerous cells that can develop anywhere in the body but are most commonly found in the skin of about 20% of dogs. They can vary greatly in appearance, and their behavior can be unpredictable, with some growing slowly and others quickly. Mast cell tumors can cause discomfort, itchiness, and other skin-related issues.


Osteosarcoma is a form of bone cancer often found in large and giant breed dogs. This aggressive cancer causes lameness and severe pain, and it can lead to fractures even from minor injuries due to the weakening of the bone structure.

Mammary Gland Tumors

These are common in unspayed female dogs. Just like human breast cancer, it can either be benign or malignant. Regular examinations of the mammary glands can help in early detection.


 Melanomas in dogs are cancerous growths that typically arise from pigmented cells in the skin but can also occur in the mouth or toes. These tumors can be aggressive and metastasize to other areas of the body.

Each type of cancer can lead to various symptoms and health problems in dogs, affecting their quality of life and lifespan. In addition, treatment options and prognosis vary depending on the type stage of the cancer, as well as the overall health of the dog.

Causes of Cancer in Dogs

Just as it is with humans, the precise causes of cancer in dogs can be somewhat elusive, often involving a mix of genetic, environmental, and lifestyle elements. However, several key factors stand out:

  • Genetic Factors – Certain breeds are more predisposed to specific cancer types, indicating genetic factors at play. For instance, Golden Retrievers are at an increased risk of developing lymphoma and hemangiosarcoma.
  • Age – Cancer risk escalates as dog’s age. An older dog is more prone to cancer development than its younger counterparts.
  • Environmental Influences – Contact with certain chemicals, toxins, or radiation can amplify the risk of developing dog cancer. A notable example is that exposure to second-hand smoke has been linked to lung and nasal tumors in dogs.
  • Viral Impact – Certain viruses, like the canine papillomavirus, are connected with developing specific cancer types in dogs.
  • Hormonal Influences – Females that haven’t been spayed are more susceptible to mammary gland tumors due to hormonal fluctuations related to heat cycles.
  • Obesity and Diet – Mirroring the situation in humans, obesity and poor dietary habits can amplify the risk of developing specific cancers in dogs.
  • Chronic Inflammation – Conditions characterized by long-term inflammation, such as chronic inflammatory bowel disease, can sometimes transition into cancer that develops in dogs, increasing the risk of gastrointestinal malignancies.

Grasping these risk factors can assist in early detection and potentially devising prevention strategies. In addition, regular veterinary check-ups and maintaining a healthy lifestyle are fundamental to ensuring a dog’s overall health, especially as the dog age and the risk of diseases, including cancer, increases.

Symptoms of Cancer in Canine

Certain types of cancer in pets can be straightforward to identify, while others can be considerably more elusive. As such, it’s crucial to promptly seek veterinary consultation if you observe any unusual changes in your pet’s health. Here are some clinical signs and warning signs of cancer in dogs that you should be vigilant about:

cancer in dogs
  • Noticeable swellings or lumps that remain constant or exhibit progressive growth
  • Sores that seem resistant to healing
  • A decrease in body weight
  • Reduced appetite
  • Unexplained bleeding or discharge from any bodily opening
  • A distinctly unpleasant odor
  • Challenges when eating or swallowing
  • Reluctance towards exercising or an apparent loss of stamina
  • Persistent lameness or stiffness
  • Difficulties when breathing, urinating, or defecating

However, remember that these clinical signs can also correspond to conditions other than cancer. Therefore, any sustained change in your dog’s health should trigger a visit to the vet for further examination. Vigilance and swift action can be crucial in detecting and treating cancer in pets early.

Diagnosis of Dog Cancer

Identifying cancer in dogs encompasses a multi-faceted approach, typically commencing with a meticulous physical examination and a thorough exploration of the pet’s health history. Here’s an overview of the standard procedures veterinary oncologists often follow to diagnose cancer –

  • Physical Check-up – The process starts with a comprehensive physical examination. The vet checks for lumps, skin color alterations, or abnormal discharge – signs that may indicate the presence of a malignant tumor.
  • Blood and Urine Analysis – Blood tests can spot systemic issues like changes in organ function, potentially indicative of cancer. Simultaneously, a urinalysis can highlight irregularities that might point toward certain types of cancer.
  • Biopsy – When a suspicious lump is detected, a biopsy may be performed, involving the extraction of a small tissue sample for microscopic examination. This procedure often provides the most conclusive diagnosis of cancer.
  • Imaging Techniques – Various imaging methods, such as X-rays, ultrasounds, CT scans, and MRIs, help detect tumors, ascertain their size and location, and check for metastasis (cancer’s spread to other body parts).
  • Specialized Testing – Additional tests might be required depending on the type of suspected cancer. For example, bone marrow tests could be utilized for potential hematologic cancers, while endoscopy might be employed to inspect internal structures.
  • Histopathology – If a tumor is surgically excised, it’s dispatched to a lab for histopathological examination. Here, a specialist scrutinizes the cells to validate the diagnosis and determine the grade and type of cancer.

Every diagnostic tool imparts valuable information to the veterinary oncologist. Occasionally, several tests may be necessary to diagnose accurately and stage cancer, which is pivotal in formulating the most effective treatment strategy.

In addition, advancements in cancer research, aided by organizations like the National Cancer Institute and the Veterinary Cancer Society, have paved the way for innovative diagnostic and therapeutic methods. Clinical trials, often involving specific dog breeds diagnosed with cancer, have become integral in developing promising new treatments.

Treatment for Dogs with Cancer

The treatment strategies for dogs diagnosed with cancer are multifaceted and largely hinge on the disease’s type and stage and the pet’s overall health. Here’s a summary of the prevalent methods employed in treating cancer in pets:


One of the common forms of treatment for several types of canine cancer, surgery aids in the physical removal of tumors, thereby eradicating or reducing the presence of cancerous cells in the body. This procedure can significantly prolong the dog’s life and enhance its quality of life. If the cancer has not metastasized and is localized, surgery might even lead to a cure.

Surgery is often supplemented with other treatments like chemotherapy or radiation to optimize outcomes. Post-operative care, encompassing pain management, wound care, and vigilance for recurrence signs, is integral for recovery.

a dog in the hospital bed


Chemotherapy entails the usage of drugs to eliminate cancer cells. It could be administered as a standalone treatment or in combination with other therapies. In addition, it might either be systemic (impacting the whole body) or localized, based on the cancer’s characteristics and extent.

Commonly used chemotherapy drugs and protocols in veterinary medicine include Cyclophosphamide, Doxorubicin (Adriamycin), Carboplatin and Cisplatin, Vinblastine and Vincristine, and Lomustine (CCNU). Each drug functions by causing DNA damage in cancer cells or inhibiting cell division or synthesis.

Radiation Therapy

As a focused treatment approach, radiation therapy employs high-energy radiation to damage the DNA of cancer cells, preventing them from multiplying and expanding. This therapy can be useful for treating localized tumors in dogs, either to reduce the tumor size or to slow its growth. However, as radiation concentrates on a specific region, side effects are often confined to the treated area and might include skin irritation or hair loss.


Immunotherapy, an innovative strategy in cancer treatment, harnesses the body’s immune system to combat cancer cells. It encompasses techniques such as vaccines, checkpoint inhibitors, and cell therapies. This approach can decelerate tumor growth, prevent cancer recurrence, and improve dogs’ overall quality of life.

Targeted Therapies

Targeted therapy is a specialized treatment that focuses on certain molecules or pathways involved in cancer growth and proliferation. Unlike traditional treatments, it aims to disrupt cancer cell function, inhibiting their proliferation and leading to their eventual demise.

Palliative Care

Palliative care is concentrated on managing the symptoms and side effects of the disease and its treatment, thus improving the quality of life for dogs with cancer. Palliative care can encompass medications to manage pain, dietary modifications to counter weight loss, and physical therapy to sustain mobility.

Clinical Trials

Clinical trials allow dogs to receive new and potentially more effective therapies before they are generally available. Participation can benefit the dog, especially when other treatments have failed or are not ideal, and contribute to a wider understanding of canine cancer.

The course of treatment will be tailored based on the type of cancer, its stage, the dog’s overall health, and its tolerance to treatment. Regular follow-ups will be necessary to monitor the dog’s response to treatment and adjust the plan. Treating cancer in pets often requires a multidisciplinary approach, including veterinary oncologists, surgeons, and radiologists, to ensure the best possible care.

Whether you’re a veterinary professional or a pet parent, the key is to be informed about the disease, the available treatment options, and how to provide the best care possible for a dog diagnosed with cancer. In emergencies, immediate care can make a significant difference. Similarly, staying abreast of the latest developments in comparative oncology can lead to breakthroughs in treatment options and improved outcomes.

Preventing Cancer in Dogs

While it’s impossible to prevent cancer completely, there are certain steps pet owners can take to minimize the risk:

  • Regular Check-ups: Regular vet visits can help in the early detection and intervention of potential health issues, including cancer.
  • Healthy Diet: A balanced, nutritious diet can strengthen a dog’s immune system and help prevent diseases. Some studies suggest that a diet rich in certain nutrients may have anti-cancer benefits.
  • Maintaining a Healthy Weight: Obesity can increase the risk of certain cancers. However, regular exercise and portion control can keep your dog at a healthy weight.
  • Limit Exposure to Carcinogens: Reduce exposure to known carcinogens like tobacco smoke, certain pesticides, and excessive sunlight.
  • Regular Vaccinations: Vaccines protect against certain viral infections that can lead to cancer.
  • Spaying/Neutering: Spaying or neutering your dog can lower the risk of certain types of cancer, such as breast or testicular cancer.
  • Regular Dental Care: Regular dental cleanings can reduce the risk of oral cancers.

Remember, prevention is always better than cure. It’s about providing the best care and attention to your dog’s health and well-being.

Frequently Asked Questions

The life expectancy of a dog with cancer varies greatly depending on several factors, including the type and stage of cancer, treatment options, and the overall health and age of the dog. Some dogs may respond well to treatment and live for several months to years, while others may have a more aggressive form of cancer that progresses rapidly.

Therefore, it is important to consult with a veterinarian who can provide a more accurate prognosis based on the specific details of the dog’s condition. Early detection, proper treatment, and supportive care can greatly improve the quality of life and potentially extend the lifespan of a dog with cancer.

The growth rate of cancerous tumors in dogs can vary depending on the type of cancer and individual factors. Some tumors can grow rapidly, while others may grow slower. Factors such as the aggressiveness of the cancer, the stage at which it is diagnosed, and the tumor’s specific characteristics can influence the growth rate.

It’s important to note that not all tumors are cancerous, and benign tumors tend to have a slower growth rate compared to malignant tumors. Therefore, regular veterinary check-ups and early detection are crucial for identifying and monitoring abnormal growth in dogs.

Determining whether a lump in a dog is cancerous requires a proper veterinary examination and diagnostic testing. While it’s impossible to diagnose cancer based on appearance alone definitively, some characteristics might raise suspicion. Cancerous lumps in dogs can vary in size, shape, and texture.

They may feel firm, irregular, or attached to underlying tissues. Rapid growth, changes in size or shape, ulceration, bleeding, or inflammation in the area can also be concerning signs. However, it’s important to note that benign lumps can sometimes mimic cancerous ones, so proper evaluation is necessary. 

The cost of cancer treatment in dogs can vary depending on various factors such as the type of cancer, stage of the disease, treatment options, location, and the individual veterinary clinic. Cancer treatment can involve various procedures, including diagnostics, surgery, chemotherapy, radiation therapy, medications, and supportive care. These treatments can be costly, and expenses can quickly increase over time.

The cost may include initial consultations, diagnostic tests, surgery or other procedures, medications, follow-up visits, and ongoing monitoring. Therefore, it is best to consult with your veterinarian or a veterinary oncologist to get an accurate estimate of the potential costs of your dog’s specific case and discuss available treatment options and financial considerations.

The decision to pursue chemotherapy treatment for a dog with cancer is a personal one that should be made in consultation with a veterinarian and possibly a veterinary oncologist. Chemotherapy can be an effective treatment option for certain types of cancer in dogs and can help to improve their quality of life and extend their survival time. However, it is important to consider factors such as the type and stage of cancer, the dog’s overall health, potential side effects of the treatment, and the dog’s circumstances and well-being.

Chemotherapy may not be appropriate or beneficial in all cases, and the potential risks and benefits should be carefully weighed. It is important to have open and honest discussions with your veterinarian to understand the potential outcomes and make an informed decision based on what is best for your dog.

Yes, there have been advancements in the treatment of cancer in dogs. Veterinary medicine has made significant progress in understanding various types of cancer in dogs, developing new treatment options, and improving outcomes. Some of the advancements include targeted therapies, immunotherapies, and advancements in surgical techniques and radiation therapy.

These advancements have improved the quality of life and increased survival times for dogs with certain types of cancer. However, it’s important to note that the treatment options and outcomes can vary depending on the type and stage of cancer and individual factors. 

Cancer can be painful for dogs depending on the type, location, and stage of the disease. Some forms of cancer can cause discomfort, pain, and other symptoms, such as difficulty eating, breathing, or moving. However, it’s important to note that not all types of cancer cause pain, and the level of pain experienced can vary among individual dogs. Therefore, monitoring your dog closely for any signs of pain or discomfort, such as changes in behavior, appetite, or activity level, is essential.

Suppose you suspect that your dog is in pain. In that case, it’s best to consult with your veterinarian, who can assess your dog’s condition and provide appropriate pain management strategies to ensure their comfort and well-being.

The final stages of cancer in dogs can vary depending on the type of cancer and its progression. As cancer advances, dogs may experience a decline in overall health and quality of life. Common signs in the final stages of cancer may include severe weight loss, loss of appetite, lethargy, difficulty breathing, pain, difficulty walking or moving, organ failure, and the spread of cancer to other body parts. Dogs may also exhibit changes in behavior, such as increased restlessness or withdrawal.

Hemangiosarcoma is known as one of the fastest-growing cancers in dogs. It originates from the blood vessels and commonly affects organs such as the spleen, liver, or heart. Hemangiosarcoma can spread rapidly and cause internal bleeding, making it a particularly aggressive form of cancer. It is often diagnosed at advanced stages, making treatment challenging. Early detection and prompt intervention are crucial for managing aggressive dog cancer. If you suspect your dog may have any cancer, it’s important to consult with a veterinarian for proper diagnosis and treatment options.

Spleen cancer, specifically hemangiosarcoma, can cause pain in dogs. As the cancer progresses, it can cause enlargement of the spleen, which can lead to discomfort and abdominal pain. Additionally, if the cancerous tumor ruptures, it can result in internal bleeding, causing acute pain and potentially life-threatening complications. However, it’s important to note that pain can vary depending on the individual dog and the cancer stage.

Therefore, pain management and supportive care are important aspects of treatment for dogs with spleen cancer to help improve their quality of life. Consulting with a veterinarian will guide your dog’s pain management strategies and treatment options.

Most types of cancer in dogs are not contagious to humans. The transmission of cancer between species is extremely rare. However, a few cases are documented in scientific literature where certain types of cancer, such as canine transmissible venereal tumor (CTVT), can be transmitted between dogs through direct contact. Nonetheless, these instances are very uncommon, and the vast majority of cancers in dogs are not transmissible to humans. It’s always important to practice good hygiene and take necessary precautions when handling or treating a dog with cancer. Still, the risk of contracting cancer from a dog is generally minimal.

Blood tests can provide some information that may suggest cancer in dogs, but they cannot definitively diagnose cancer. Blood tests can detect certain abnormalities that may indicate the presence of cancer, such as changes in white blood cell count, red blood cell count, liver enzymes, or tumor markers. However, further diagnostic tests, such as imaging (X-rays, ultrasound, etc.) or tissue biopsy, are typically required to confirm a cancer diagnosis in dogs. These additional tests help determine the location, extent, and specific type of cancer present. A veterinarian will assess the overall clinical picture and use a combination of tests to diagnose cancer in dogs accurately.

The exact cause of bladder cancer in dogs is often unknown. However, certain factors may increase the risk of developing this condition. These can include exposure to certain carcinogens, such as environmental toxins or chemicals, chronic bladder infections or inflammation, certain breeds being more predisposed to bladder cancer (such as Scottish Terriers), and genetics may also play a role. It’s important to note that while these factors may increase the risk, not all dogs exposed to them will develop bladder cancer, and some dogs without these risk factors can still develop the disease. Therefore, early detection and timely treatment are crucial for managing bladder cancer in dogs.

Cancer itself typically does not directly cause diarrhea in dogs. However, certain types of cancer or cancer treatments may indirectly contribute to the development of diarrhea. For example, tumors in the gastrointestinal tract can obstruct or affect the normal functioning of the digestive system, leading to digestive issues, including diarrhea. Additionally, certain chemotherapy drugs used to treat cancer may cause gastrointestinal side effects, including diarrhea.

The exact cause of bone cancer, osteosarcoma, is not well understood in dogs. However, some factors may poorly contribute to its development. For example, certain dog breeds, such as larger and giant breeds, are more prone to developing bone cancer. Genetic factors may also play a role, as there is some evidence of a hereditary component. Additionally, previous bone trauma or injury, exposure to certain environmental factors, and rapid bone growth during puppyhood have been suggested as potential risk factors. However, more research is needed to understand the causes of bone cancer in dogs fully.

Yes, dog cancer can sometimes cause increased thirst, known as polydipsia. Certain types of cancer, such as kidney or tumors affecting the endocrine system, can disrupt the body’s normal functioning and increase water consumption. Therefore, monitoring changes in your dog’s drinking habits is important and consult a veterinarian if you notice excessive thirst or other symptoms. Increased thirst can also be associated with other health conditions, so a proper evaluation by a veterinarian is necessary to determine the underlying cause.

The texture of cancerous lumps in dogs can vary. They can be either hard or soft, depending on the type and location of the cancer. Some cancerous lumps may feel firm and solid, while others may be softer or have a more irregular texture. It’s important to note that not all lumps or tumors in dogs are cancerous, and a proper diagnosis by a veterinarian is necessary to determine the nature of the lump.

Yes, cancer in dogs can sometimes lead to kidney failure. Certain types of cancer, such as renal cell carcinoma or lymphoma, can directly affect the kidneys and interfere with their normal function. In addition, cancer treatments like chemotherapy can also have side effects on the kidneys and potentially contribute to kidney damage. Therefore, it’s important to monitor kidney function in dogs with cancer and work closely with a veterinarian to manage potential complications or changes in kidney health.

Yes, cancer in dogs can cause anemia. A low red blood cell count or decreased hemoglobin levels characterize anemia. In dogs with cancer, anemia can occur due to various reasons. For example, cancer can produce abnormal or dysfunctional red blood cells, cause blood loss due to tumor growth or bleeding, or affect the bone marrow’s ability to produce enough healthy red blood cells. Additionally, some cancers can infiltrate or affect red blood cell production organs, such as the bone marrow or spleen. Anemia can contribute to weakness, fatigue, pale gums, and other symptoms in dogs with cancer, and it’s important to address and manage this condition as part of the overall treatment plan.

Neoplasia, which refers to the abnormal and uncontrolled growth of cells, is relatively common in dogs. However, the frequency of cancer, a type of neoplasia characterized by malignant cells, can vary depending on several factors such as breed, age, genetics, and environmental factors. For example, certain dog breeds are known to be predisposed to specific types of cancer, and older dogs have a higher risk of developing cancer than younger ones. Environmental factors such as exposure to certain chemicals or carcinogens can also influence cancer incidence. While cancer is a significant health concern in dogs, it’s important to note that not all neoplasms are cancerous, and many benign tumors can be successfully treated or managed. 

The specific side effects of cancer treatments can vary depending on the type of treatment used and the dog’s response. Chemotherapy, for example, can have side effects such as gastrointestinal upset, decreased appetite, nausea, vomiting, and temporary immune system suppression. Radiation therapy may cause skin irritation or burns in the treated area. Surgery can result in pain, wound healing complications, and potential loss of function if a limb or organ is removed.

It’s important to note that while cancer treatments can have side effects, the goal is to balance the potential risks with the benefits of treating cancer. The impact on your pet’s quality of life will depend on various factors, such as the type and stage of cancer, the dog’s overall health, and the treatment’s effectiveness. In some cases, the side effects may be temporary and manageable, while in others, they may be more significant. Your veterinarian will work closely with you to discuss the potential side effects, monitor your pet’s response to treatment, and make adjustments as needed to optimize their well-being and quality of life throughout the treatment process.

While cancer can affect dogs of any breed, certain breeds are known to have a higher predisposition to certain types of cancer. Some dog breeds that are more prone to developing cancer include:

  1. Golden Retrievers: They have an increased risk of developing various types of cancer, including lymphoma, hemangiosarcoma, and mast cell tumors.
  2. Boxers: They are predisposed to several types of cancer, including mast cell tumors, lymphoma, and brain tumors.
  3. Bernese Mountain Dogs: They have a higher incidence of certain cancers, such as histiocytic sarcoma, mast cell tumors, and osteosarcoma.
  4. Rottweilers: They are prone to developing osteosarcoma, bone cancer, and lymphoma.
  5. Great Danes: They have an increased risk of developing bone cancer, specifically osteosarcoma.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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