CLEAR Education

Below is a breakdown of common canine cancers. We hope this provides insight, information, and advice on how to handle these cancer types and its effect on our four legged friends. We will update and add material to this page as we have it prepared or new industry findings emerge.

What is Canine Lymphosarcoma (Lymphoma, LSA)?

Lymphoma is one of the most common cancers of dogs. It is a cancer that derives from the cells in the lymph system, which is comprised of the lymph nodes and circulating lymphocytes in the vascular system. Although lymphoma can affect virtually any organ in the body, it most commonly arises in organs that function as part of the immune system such as the lymph nodes, spleen, and bone marrow. By far the most common type of lymphoma in the dog is multicentric lymphoma, in which the cancer is usually first noticed in lymph nodes. Lymphoma is also one of the most well understood cancers in dogs, with regard to diagnosis, treatment options, and prognosis. It is one of the few cancers in dogs that can have remission times of years, and although it is not frequent, a cure is sometimes a possibility.

The Causes of Canine Lymphoma

The cause of lymphoma is not well understood. Certain breeds of dogs, such as Golden Retrievers, are at higher risk of getting lymphoma. Therefore, it is believed that there is a significant genetic component to lymphoma. However, any breed of dog, at any age, including juvenile dogs, can get lymphoma. It is also believed that there are environmental contributors to lymphoma. Environmental factors such as chemicals, airborne pollutants, and other variables may damage cells. As dogs age, cellular repair is slower, and cancer becomes more prevalent. Other than protecting our dogs from known predispositions or causes of cancer such as secondhand smoke, or certain chemicals, we really cannot prevent our dogs from getting lymphoma.

Symptoms of Canine Lymphoma

The symptoms of lymphoma are variable and tend to mimic the symptoms of many other diseases or disorders, but will also depend on the cancer’s location and how advanced it is. Commonly observed findings are pronounced enlargement of the lymph nodes on the underside of the dog’s neck, slightly behind the chin. Dogs may also show signs of one or more of the following:

  • Weight loss
  • Lethargy
  • Loss of appetite
  • Constipation
  • Vomiting
  • Diarrhea
  • Shortness of breath
  • Fever
  • Increased thirst
  • Increased urination
  • Difficulty swallowing
  • Skin nodules or masses

Detection and Staging

Lymphoma can be detected via several pathways.  Sometimes, a dog is just not feeling well. Sometimes an owner or a veterinarian detects enlarged lymph nodes.  Sometimes a veterinarian will detect an abnormal finding on a routine physical exam, such as an enlarged spleen or liver.

When a dog is diagnosed with lymphoma, and is feeling ill (the dog is showing signs of loss of appetite, weight loss, lethargy, or the like) this means that the lymphoma is classified as “b”.  This does not refer to the type of lymphoma, but merely to the fact that the dog feels ill.  If lymphoma is diagnosed and the dog feels well (no noticeable symptoms of illness), then the lymphoma is classified as “a”.  Dogs that are diagnosed with lymphoma generally tend to respond more favorably to treatment if they are feeling well (a).   However, depending on the stage and type of lymphoma, dogs that are ill (b) may respond very favorably to treatment as well.

There are five stages of lymphoma in dogs.  They are classified as stages I through V. These stages are identified based on diagnostic tests such as physical exam, blood work, radiographs, ultrasound and bone marrow biopsy.  Additional blood or bone marrow testing may further identify lymphoma as B or T cell lymphoma.  The stages of lymphoma in dogs are essentially as follows:

  • Stage I – only one lymph node (or lymphoid tissue in one organ) is involved
  • Stage II – multiple lymph nodes or a chain of lymph nodes in a localized area are involved
  • Stage III – Widespread, generalized lymph node involvement; most or all peripheral lymph nodes are affected
  • Stage IV – any or none of the above, plus liver and/or spleen involvement
  • Stage V – any or none of the above, with bone marrow involvement, blood involvement or involvement of any non-lymphoid organ

All of this information is distilled onto a classification of the general disease.  For example, a dog may be diagnosed with Stage IV b, B cell lymphoma.  This means that the liver and spleen have cancerous cells in them (indicating systemic metastasis), that this dog is feeling ill from the lymphoma, and that the B cell lymphocytes are the cell of origin.  Another example would be stage V b T-cell lymphoma.    The higher the stage number, the more disseminated the cancer cells are throughout the body.  The cell type can be important, as B and T cell lymphomas behave differently, and respond differently to chemotherapeutic treatment.


Depending on the age of diagnosis, and the stage and type of lymphoma, the diagnosis of lymphoma is not a death sentence.  In fact, lymphoma is amongst the most highly treatable cancers that occur in dogs.

The mainstay of treatment for dogs with lymphoma is the administration of chemotherapy. Chemotherapy is the use of chemicals (medication) to treat disease – more specifically; it usually refers to the destruction of cancer cells. The best responses in terms of length of tumor control and survival are generally seen with protocols that entail administration of more than one chemotherapy drug, although there are approaches that involve administration of a single drug.

In the treatment of dogs with cancer it is usually to put the disease into remission to prolong life and to assist in a better quality of life.  Chemotherapy protocols are complicated and rapidly evolving.  A veterinarian oncologist is the best person to discuss your options and advice on treatment for canine lymphoma.

Another form of treatment less commonly used is radiation. The exploration of radiation therapy, used in conjunction with chemotherapy is finding new avenues in the treatment of canine lymphoma.  Early research suggests that the combination of the two improve remission rates and can extend the disease free interval in dogs with multicentric malignant lymphoma.

There are quite a few options for treatment of lymphoma.  They range from very inexpensive medications that will often create a state of remission for a short time, to more impactful, costly therapies that can drastically increase median survival time.  More aggressive chemotherapy is associated with an increased risk of adverse effects such as nausea, malaise, or infections secondary to immune suppression.  The more aggressive protocols are also more costly, and more intensive.  However, overall, the more aggressively lymphoma is treated, the longer your dog will survive.  In spite of the possibility of adverse side effects, many dogs have a very good quality of life for the majority of treatment.  “Bumps in the road” such as infections, or nausea, can be dealt with medically most of the time.  Finances are a fair consideration, and it is very important that dog owners make these choices with finances in mind.  Many dog owners feel guilty if they cannot afford the most ideal treatment option.   However, veterinarians understand this consideration, and support any decision that an owner makes that is well informed and honest. It is important to make the best decision that is feasible, and to place positive energy toward that path.


If your dog is diagnosed with lymphoma, obtain all the information that you can. Speak with your veterinarian about treatment options. Inquire as to whether a veterinary oncologist might be helpful. Consider your personal finances with the respect that they are due, and realize that your choice is multi- factorial, and does not directly reflect the degree of love that you have for your dog. Each patient is an individual, as is the owner of each dog that is ill.

Partner with your Veterinarian for Early Detection

You and your veterinarian are partners in keeping a watchful eye on your pet’s health.  Paying close attention to your pet’s habits will key you in when there may be a problem.  Pay attention to those impressions that your pet seems “off”.  Make a routine of checking your pet’s gum color, eyes, ears and mouth.  Run your hands over their body periodically to make sure there are no new growths or tender areas.  Weight loss may be evident over the spine and ribs.  Bring your concerns to your veterinarian, especially if it they have not had a checkup within the past 6 months to a year.  Remember that a year in a dog’s life is equivalent to 7 or so years in our life.  This is why a good physical exam should be conducted yearly on a dog in their early years of age and twice when over 7(when they hit their fifties!).

Before visiting your veterinarian, write down all of your concerns and questions.  As our pet’s advocate, this is so important as we are their voice and we tend to forget when the consultation begins.  After a medical history is taken, the physical exam begins.  A good physical examination by your veterinarian will include palpation of lymph nodes, oral exam, chest auscultation and palpation of the abdomen for abnormalities and evidence of bone or joint pain.  Blood work and urinalysis may be recommended to screen for internal organ dysfunction.  A fine needle aspiration may be conducted of lumps to determine their nature.  Many soft tissue tumors turn out to be benign lipomas (a benign tumor made up of fatty tissue).  These are usually not a problem unless they are in an area that causes a problem with mobility (the arm pit or near a joint).  It is good to check these and document that they are not problematic and it gives one peace of mind.  Don’t just assume a mass is a lipoma.  Have it checked out.

Taking an Holistic Approach

It is important to take a holistic approach to cancer treatment.  You may choose to consult with a veterinary oncologist, a specialist in cancer medicine for dogs and cats.   They can present the latest research and treatments offered in Western veterinary medicine.  Isn’t it interesting to note that many chemotherapy and anti-infective agents are derived from natural origins?    Herbal medicine has a multitude of compounds that are helpful in treating and preventing cancer such as turmeric, green tea/polyphenols, mushroom polysaccharides and a multitude of others.  It is overwhelming looking in to supplements for treating cancer and they can easily take over your pet’s food bowl.  There are so many that are potentially helpful and how do you know their quality and efficacy?

A holistic veterinarian trained in herbal medicine, acupuncture, homeopathic medicines and other complementary modalities can help look at your pet’s unique situation and help prioritize which therapies would be most helpful.  They should coordinate alternative therapies with your conventional veterinarian or oncologist.  They can also guide you in the selection of a diet that is suitable for cancer patients.  Cancer tends to take over the metabolism and cause weight loss.  It is important to feed a diet that has fewer carbohydrates and more quality protein as well as antioxidants and omega fatty acids. There are many resources available such as acupuncture for pain, nausea caused by chemotherapeutic agents and to improve overall well being.  To find a holistic veterinarian certified in these modalities you can go to:


Protecting Your Dog

One of the most difficult tasks a veterinarian faces is to inform a pet owner that their beloved friend has cancer. Pet owners are faced with this diagnosis more often than you would think. It is estimated that 50% of dogs will be diagnosed with cancer at some point in their lifetime.

Today’s pets are living longer due to an increased focus on preventive medicine. In addition advances in medicine have also added to pets living longer than ever, thus opening the door to age related conditions. Environmental influences such as toxins (pesticides, herbicides and air pollutants), processed foods, and food additives, vaccinations and genetic influences have all been blamed as causative factors.

There are many factors that can help decrease the likelihood of cancer: (annual wellness examinations), judicious vaccination, diet, exercise, avoidance of potential toxins in the environment and of course, good genes. Just like anything else in life, there is no guarantee of health despite our best efforts to maintain it. What we do know is that pets have demonstrated an overall positive effect on our health. They help increase our physical and mental health by their mere presence. We gladly do our best to promote theirs.

What are Canine Mast Cell Tumors?

Canine mast cell tumors (MCTs) are a common malignant tumor in dogs. Mast cell tumors are regulators of the immune system cells. While MCTs can be found in many organs of the body, it is the most common malignant skin tumor in dogs.

The normal mast cells are important in inflammation and allergic reactions. The MCTs themselves however, are formed by many trillions of malignant mast cells. They become malignant by mutating in a way that allows them to escape the natural process of cell aging and death. For that reason they are able to grow unchecked, and these tumors can range from relatively benign to being very aggressive.

Malignant mass cells are also not as stable as the normal mast cells. Each cell contains many substances that can cause bruising, bleeding, swelling, and inflammation. Any trauma directly to the tumor such as surgery, scratching, bumping, or crushing the tumor may cause release of inflammatory mediators. In this situation the patient may display symptoms of an allergic reaction without any contact with allergens or parasites.

The Causes of Canine Mast Cell Tumors

It is hard to find a definitive cause, but the thought is that genetics plays a part in this type of cancer. There are certain breeds that can be more affected, such as Labrador Retrievers, Golden Retrievers, Bulldogs, Boxers, Boston Terriers, Cocker Spaniels, Schnauzers, and Shar-peis.

Symptoms of Canine Mast Cell Tumors

Symptoms can vary depending on the location of the tumor. Some dogs present for just a mass on or under the skin whereas others have clinical signs related to the chemicals that are released by the tumor that may cause bruising, bleeding, swelling, inflammation and stomach ulcers. Affected dogs may experience fatigue, decreased appetite, increased respiration, diarrhea, or vomiting. Also, if the MCTs are disturbed and those previously-mentioned mediators leak out, the dog might show shock-like symptoms; severe lethargy, vomiting, pale gums, vomiting, decreased appetite, or collapse, and/or stomach ulcers. Mast cell tumors can look like anything and are often mistaken for benign fatty growths called lipomas.

Detection and Staging

A biopsy technique called a needle aspirate can be quite helpful in determining a MCT from any other benign or malignant process. The cells have a certain appearance which makes them easy to discern, making an initial diagnosis possible. Still, the sample will most likely be sent to the lab for a more definite finding, and to establish the next course of action.

Staging will find out the overall health of the dog in question as well as determine the stage of the cancer and whether or not it has spread to several areas. Everything depends on each individual case as to what is done. Minimal staging usually consists of routine blood work, urinalysis, and a lymph node evaluation.

Maximum staging includes additional blood work, an ultrasound, and aspiration and cytology of certain internal organs. Again, the determination as to what is done depends on the health of the patient, the size and location of the tumor, the grade of the tumor (explained below), the number of tumors detected, and the lymph node status.


Unless the tumor is too big to remove or has spread systemically, almost all MCTs require surgery. There are two grading systems.

The first divides the tumors into those that are unlikely to spread (grade I), moderately likely to spread (grade II) and highly likely to spread (grade III). Grade I tumors are often cured with surgery whereas grade III tumors may be best treated with appropriate surgery and additional treatment to treat and prevent spread of the tumor.

A more recent, simpler grading system is a two tier system: Those tumors that are unlikely to spread and that can and should be cured with appropriate local therapy alone, or those that have a high risk of spreading and thus can be difficult to control unless the local tumor is treated and additional medicines are used to delay or prevent tumor regrowth and spread.


Remember, dogs tolerate both chemotherapy and radiation better than we do. Quality of life is of utmost importance. There are drugs that can be given to effectively counteract any adverse affects an individual dog might have so they will be comfortable throughout their treatment.

What is Canine Hemangiosarcoma?

Canine hemangiosarcoma or HSA, is a cancer that develops in the cells that form blood vessels (endothelial cells). Interestingly, dogs are the species that are the most diagnosed with this type of cancer. It is estimated that as many as two million dogs get this cancer. Most will unfortunately die from HSA, as the disease is usually incurable. There is one form of HSA that is generally less aggressive, and that is cutaneous melanoma. The cause has been attributed to exposure to the sun, and is generally treatable with surgery.

Dogs are usually middle-aged and older when they develop the disease, and some breeds are known to be predisposed to HSA. German Shepherds, Golden Retrievers, Portuguese Water Dogs, and Skye Terriers are four of them. That being said, any breed and sex can develop HSA.

The Causes of Canine Hemangiosarcoma

Much more research is needed for this type of canine cancer. Sun exposure and genetics appear to result in an increased risk of developing this tumor. The exact cause is unknown.

Symptoms of Canine Hemangiosarcoma

The biggest problem with this disease is that the symptoms can mimic a benign tumor such as a hematoma, or an inability to clot blood, such as seen when a dog ingests rat poison. Quite often you do not even know the tumors are present until a bigger problem presents itself, such as blood loss from a ruptured spleen or liver. They are frequently painless as well, which makes detection of an issue difficult.

Clinical signs that the family might notice include pale gums, rapid breathing, an acute weight gain due to fluid, often blood, in the abdomen, extreme fatigue or lethargy, and eventual collapse. These tumors can grow and then rupture. Since the tumors develop in the cells that form blood vessels, the ruptures cause acute bleeding. That brings on the symptoms mentioned above here. While blood is not seen outside of the dogs’ body, a sick dog is losing blood internally.

Detection and Staging

The staging generally consist of a minimum of blood work, three-view chest X-rays, abdominal and heart ultrasound, and urinalysis. There may be other tests ordered, or the animal may arrive in a state of shock due to internal bleeding, necessitating immediate supportive care prior to surgery; IV fluids, pressure wraps to help stop bleeding, and blood pressure checks, for example.

Surgery is usually recommended, mainly because there is really no other way to see for sure if a mass is malignant or not. It is also the only way to stop a patients internal bleeding. This not only can save the dogs’ life at this particular time, but a tissue sample can be taken to confirm a diagnosis of HSA.


Hemagiosarcomas can occur anywhere in the body and may present as a mass on sites such as the spleen, liver, muscle, heart, under the skin, on the tongue and on the skin. Surgery is the single most effective treatment for patients with hemangiosarcomas. Unfortunately, for most patients, it is not possible to determine the cause of the bleeding until the mass is evaluated by a pathologist after it was removed. For example, for dogs with a mass on the spleen, 2/3rds of them are malignant, one third is not. Of the two thirds of the dogs with a malignant splenic mass, two thirds of them have hemangiosarcoma. To make things more difficult, not all hemangiosarcomas are the same; some are low grade with a more favorable prognosis, whereas others are intermediate and high grade hemangiosarcomas. The high grade tumors are generally quite aggressive.

Thus, even though surgery may be essential to save the dogs’ life in a crisis, it is rarely the only answer. Since hemangiosarcoma is a very aggressive disease, the life expectancy after surgery may be a few weeks to a few months. Chemotherapy is generally recommended after surgery, since this cancer metastasizes early and quickly. Doxorubicin based chemotherapy is used most commonly.


The average survival time for dogs with a malignant hemangiosarcoma after both surgery and chemotherapy may be only six to eight months. A great deal of research is underway to find new treatments for this very aggressive disease.

What is Canine Osteosarcoma?

Osteosarcoma is the most common type of bone cancer in dogs. It can occur anywhere on the skeleton, however it is most commonly diagnosed at the end of the bones (metaphysis) of the legs. This cancer has many similarities to osteosarcoma in children. It is painful in both kids and dogs. It almost always metastasizes (spread) to other organs, especially the lungs and other bones. It is said that up to 85% of tumors originating in the skeletal system is osteosarcoma. Osteosarcoma as a rule becomes evident in the later years when a dog is between the ages of 7 to ten.

The Causes of Canine Osteosarcoma

Canine osteosarcoma occurs most commonly in large or giant breeds, such as Great Danes, Scottish Deerhounds, Rottweilers, and Greyhounds. The risk also seems to increase when young dogs are fed diets that promote rapid growth.

Symptoms of Canine Osteosarcoma

Most dogs with osteosarcoma have a history of acute lameness or pain. Since osteosarcoma is frequently found in the bones that may be around or involving the shoulder, knee, and wrist, the first visible symptom is lameness in the affected leg. There might also be some swelling, inflammation, and/or tenderness near the region of the tumor. The dog might also be lethargic and not want to eat. Sometimes the dog will have a growth on their body as well. Other symptoms that might be observed are:

Pain (often severe)
Broken bones at the tumor site (called “pathologic fractures”); caused by bone weakness from the cancer; usually no history of physical injury to the area
Swollen upper jaw (maxilla); usually painful
Swollen lower jaw (mandible); usually painful
Pain when opening the mouth
Nasal discharge
Swelling and pain along the spine
Swelling and pain around the ribs
Difficulty eating or chewing (dysphagia)
Respiratory distress (difficulty breathing; dyspnea); typically caused by rapid spread [metastasis] of the cancer from bone to lung tissue; can also be caused by osteosarcoma of the ribs)

Detection and Staging

If the symptoms presented to the veterinarian are lameness, pain, and/or swelling and other issues have been ruled out. Frequently osteosarcoma has a characteristic appearance noted when X-ray images are acquired. Lesions are often detected along the bone, both destructive and productive.

The process of determining the extent of the disease is called staging. Staging is completed with a series of diagnostic tests, to try to determine where else the cancer might have spread. Minimally this will normally include some routine blood work, urinalysis, three-view chest x-rays or CT scan (to look for metastatic disease), and palpation and evaluation of other bones in the body. An abdominal ultrasound may be of help to the veterinarian to determine the course of action, as is a biopsy and/or needle aspirate, which is then sent to a pathologist. This will establish the type of tumor present.

Finally, a simple test to determine whether or not the tumor has spread to other bones might be suggested. This is called a bone scan, and might require an overnight hospital stay.


Two challenges exist when caring for a pet with osteosarcoma. The first is how to treat the bone tumor itself. The second is how to delay or prevent recurrence or spread of the tumor. Regardless of the treatments chosen, every attempt must be made to ensure that the patient is comfortable with analgesics (e.g., Piroxicam, tramadol, gabapentin, etc.) without any nausea or diarrhea. Finally, it is very important to ensure that nutritional support be addressed by ensuring a diet that is relatively low in simple carbohydrates with moderate levels of high quality proteins, relatively low amounts of red meat fats and relatively high levels of fatty acids from fish or algae sources that contain docosahexaenoic acid.

If there is no evidence that the osteosarcoma has spread, the most common recommendation is surgery to remove the lesion, or to treat the tumor with radiation. If surgery is selected, then removal of the limb is the quickest, least expensive, most effective way of alleviating pain and removing the cancer. The surgery is not a complicated one, and dogs are usually up and around very quickly – and don’t forget that dogs do very well with only three legs! Another surgery that might be considered is called limb sparing surgery. In this procedure, the tumor is removed without removing the limb.

An alternative to removal of the limb via amputation or limb sparing surgery is palliative or definitive radiation therapy. Palliative radiation is given in a few (2-5) dosages to first provide comfort, second to slow the rate of progression of the tumor, and third to occasionally reduce the size of the mass. Definitive radiation therapy is done to have longer term control of the tumor by administering smaller doses of radiation more frequently, or stereotactic radiosurgery (SRS). SRS allows a higher dose of radiation to be delivered to the tumor with a low chance of damage to the surrounding tissue. SRS is only available in some select cancer centers.

Once the tumor itself is addressed with surgery or radiation, then recommendations are often given to delay or prevent recurrence and spread of the tumor. There are other drugs that can also be given in the case of a dog who is not tolerating the chemotherapy very well due to nausea and other issues, but most dogs do well without that type of intervention.


The most important thing to remember when treating this type of canine cancer is the dogs’ quality of life. When appropriate treatment is employed, the average dog will survive from 10-14 months, and be able to enjoy a good to excellent quality of life for most of that time.

What is Canine Mammary Carcinoma?

Breast cancer in female dogs and in women is common. The disease in dogs is more commonly known as canine mammary carcinoma or mammary gland adenocarcinoma. This tumor is the most common cause of death and the most common cancer in the unsprayed dog. The tumor is also quite common in dogs that were spayed late in life because exposure to female hormones early in life increases the prevalence of this tumor. About half of mammary tumors are malignant and about half of the malignant tumors have metastasized at the time they are first diagnosed. The great news is that most dogs with breast tumors are cured with appropriate surgery.

The Causes of Canine Mammary Carcinoma

As mentioned above, it is the non-spayed female that is the most likely to develop this cancer. This is especially true as the dog ages. Of the dog is spayed before her first heat (estrus) the risk of canine mammary carcinoma is only 0.05% – very low. After the first heat cycle it goes to 8%, and climbs dramatically to 26% if spayed after the second estrus. In contrast, male dogs are only at a 1% or less risk for this cancer.

If a dog is spayed after initial diagnosis, some studies show that the survival rate is higher than those who remain intact after diagnosis.

Symptoms of Canine Mammary Carcinoma

The most common clinical sign includes one or more masses or a thickening of the breast tissue. There may be discharge from the nearby nipple. Most breast tumors do not spread and most are cured with surgical resection of the tumor.

While most dogs with breast tumors are cured, a small percentage of tumors are aggressive, including a rare type of mammary carcinoma called inflammatory carcinoma This uncommon form of the disease is not only highly aggressive but progresses very fast. Its symptoms mimic mastitis (mammary gland inflammation). The skin will often be red, swollen, inflamed, and painful. These tumors are highly metastatic and warrant a grave prognosis.

Detection and Staging

Most frequently a bump or mass is found in a routine wellness exam, or by a groomer or the owner themselves. They generally start small and grow. It is not uncommon to find more than one tumor, since estrogen exposure promotes tumor growth as the years go by.

Blood work, including a CBC and chemistry screen should be done, as well as three-view chest X-rays, urinalysis, and a lymph node biopsy, if possible. In some cases, ultrasound of the abdomen is also recommended.

As with breast cancer in humans, early detection is the key to successful treatment and a positive outcome.


Surgery is the first line of defense for mammary carcinoma. The prognosis however, depends on several factors; the size of the tumor, the type, the grade, and the presence of metastatic disease. In cases that are more advanced, tumors that are more aggressive, or tumors that involve the lymph nodes, chemotherapy will more than likely also be recommended. The hope here is to reduce the risk of recurrence and spread of the disease.


Always remember, the most important thing to beat mammary carcinoma is early detection. Keep up with those wellness checks, and examine you pet often, looking for anything out of the ordinary. Also, if your dog is acting at all abnormal (for that individual), better safe than sorry. Take it to a vet to be looked at.