cancer in cats

Types of Cancer in Cats – Symptoms, Causes, Diagnosis And Treatments

Defining Cancer in Cats

Cancer in cats, medically referred to as “neoplasia,” is defined as a malignant cellular tumor. A tumor, which is an overgrowth of abnormal cells and/or the transformation of good cells into bad cells, can be either benign or malignant.

Benign (which is good and means that they are usually harmless), or malignant (which is bad and means that they are invasive and tend to spread from one part of an animal’s body to other areas, which is called “metastasis”). Malignant tumors almost always eventually cause death.

Most cancers are more common in older cats and those that are not neutered or spayed, although lymphoma tends to target younger animals. Cats infected with the feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) are at an increased risk of developing cancer.

Types of Cancer in Cats


Lymphoma, also called lymphosarcoma, is an aggressive type of cancer that involves rapid division, transformation and spread of white blood cells called “lymphocytes”. It is common in cats – especially those infected with the feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV).

Males seem predisposed to developing lymphoma. It also is more common in house cats exposed to cigarette smoke. Lymphoma often targets the digestive tract (stomach, small intestine, large intestine, rectum), spine and tissues in the chest cavity. The lymph nodes, spleen, liver and bone marrow can also be involved.

The symptoms of lymphoma depend upon which organs are affected. If diagnosed and treated early, lymphoma often can be well-managed. Many cats achieve complete remission after a course of chemotherapy. Without treatment, the prognosis is poor.

Breast Cancer

Cats usually have four pairs of mammary glands. Malignant tumors of those glands are common in older unspayed females and are the third most prevalent type of cancer in domestic cats.

Siamese cats and females with calico coats are predisposed to developing breast cancer. Most mammary tumors are adenocarcinomas that start in the cat’s front mammary glands, although the back glands certainly can be affected.

Approximately 90% of feline mammary masses are aggressively malignant, which means that they spread fast and far, often to the lungs and lymph nodes. As breast cancer progresses, the tumors can ulcerate and rupture, becoming quite painful.

Surgical removal is the treatment of choice for all cats with breast masses, although surgery won’t cure the condition if the cancer has already spread. Chest X-rays (radiographs) should be taken before deciding whether to perform a mastectomy. Chemotherapy can be helpful in some cases.

The outlook for cats with mammary cancer depends on how early it is caught and the size of the tumors when they are discovered.

Skin Cancer

Skin cancer is common in cats. Many skin tumors are benign (harmless), while others are malignant (dangerous). The most common types of feline skin cancer are basal cell carcinomas, squamous cell carcinomas, mast cell tumors, melanomas and fibrosarcomas.

Skin masses can be small or large, soft or firm, above or under the skin and solitary or clustered. They can grow slowly or quickly. Many skin tumors spread if they aren’t taken off surgically.

Removed tissues are sent to a pathology laboratory to identify the type of cancer involved. Skin cancer is mainly seen in older cats. It tends to show up on the legs, mouth, tongue base, lips, nose, ear tips, face, back and/or chest.

Basal Cell Carcinoma

Basal cell carcinoma usually presents as a solitary growth that may or may not be pigmented and occasionally ulcerates (bleeds). It can occur in clusters. Basal cell tumors can be found almost anywhere on cats and are especially common on the face, back and upper chest areas.

Most feline basal cell tumors are benign, which means that they don’t spread. They still should be removed. Persian cats are predisposed to developing a malignant form of basal cell skin cancer; any bumps on a Persian should be taken seriously.

Squamous Cell Carcinoma

Squamous cell carcinomas, also called epidermoid carcinomas, typically present as ulcerated, crusty, weeping, necrotic, non-healing cauliflower-like or hard flat growths. They tend to show up on a cat’s ear tips, lips, nose, eyelids and in the mouth.

They can be exacerbated by exposure to sunlight, especially in white or very lightly pigmented cats with pink skin. Complete surgical excision is the treatment of choice; radiation is helpful if the masses can’t be successfully removed. Chemotherapy is also an option.

Mast Cell Tumors

Mast cell tumors are fairly common, representing about 20% of all feline skin cancers. Young Siamese cats have a higher incidence of mast cell tumors than do other cats. These tumors can be single or multi-nodular growths that eventually release histamine and other irritating substances, causing gastrointestinal ulcers, skin lesions, itchiness and other symptoms.

Mast cell tumors are most common on the belly, hind legs and scrotum. They can spread to other areas, such as the spleen. Mast cell masses should always be treated as soon as they are diagnosed. Treatment options include surgery, radiation, chemotherapy and administration of steroids.


Fibrosarcoma is an aggressive and highly invasive type of cancer that originates in fibrous connective tissue. In cats, it is often associated with the feline leukemia virus, the feline immunodeficiency virus or administration of vaccines.

Fibrosarcomas tend to occur as solitary skin masses on the head, in the mouth, on the trunk or on the legs. There is some association between certain inactivated feline vaccines and development of fibrosarcomas at the injection site.

However, the potential for vaccine-associated reactions shouldn’t deter owners from vaccinating their cats. Surgical removal of fibrosarcomas is often possible. However, without wide clean surgical margins, these tumors often recur.

Causes and Prevention of Cancer in Cats

Causes of Cancer in Cats

Cancer is one of the leading causes of death in domestic cats. Technically, cancer is defined as one or more malignant tumors. A malignant tumor is a lump or growth that involves rapid cell division and that spreads through the animal’s bloodstream and/or lymphatic system, ultimately infiltrating remote areas of its body.

Many people worry that any and every tumor is “cancer,” including bumps or swellings. This is not the case. Often, these are called “benign” masses, which grow slowly and don’t invade and destroy outlying tissues. Certainly, genetic and environmental factors can influence whether or not a cat gets cancer, as can the natural course of aging.

Exposure to secondhand smoke, radiation, chemicals and herbicides can increase a cat’s risk of getting certain types of cancer. Cats infected with the feline leukemia virus (FeLV) or the feline immunodeficiency virus are predisposed to getting cancer.

Some of the more common forms of cancer in cats are lymphoma, leukemia, mast cell tumors, squamous cell carcinoma, basal cell carcinoma and soft tissue fibrosarcoma. Each of these can present in multiple ways, with varying frequencies and degrees of severity.

Common sites of cancer in cats are the skin, blood cells, mammary glands, lymph nodes, digestive tract and mouth. Despite intensive research in both the companion animal and human arenas, feline cancer is still largely an unpredictable phenomenon that is heavily influenced by hereditary, environmental and other unknown factors.

Preventing Cancer in Cats

Unfortunately, until scientists discover and truly understand what causes cats to get cancer, owners and veterinarians won’t be able to do a lot to prevent it from occurring. Regular veterinary visits can help identify any lumps or bumps on a cat’s skin, in its lymph nodes or in its mouth, so that they can be diagnosed and treated as quickly as possible.

Surgery, radiation, cryotherapy, hyperthermy, immunotherapy and chemotherapy are available at certain specialized veterinary clinics and veterinary teaching hospitals. Spaying or neutering can reduce the risk of certain types of feline cancer.

Feeding a high-quality, palatable and nutritious diet will help keep cats in good overall health, reduce their risk of contracting infectious diseases and developing other disabling disorders. With prompt diagnosis, aggressive treatment and ongoing supportive care, including pain management and long-term dietary support, many cats with cancer can live comfortable and relatively normal lives.

Special Notes

Early diagnosis of cancer always improves the prognosis. Surgery, radiation and chemotherapy are available at specialized veterinary hospitals to treat feline cancer.

With prompt diagnosis, aggressive treatment and ongoing management, including pain management and dietary support, many cats with cancer go on to live long, comfortable, and relatively normal lives.

Symptoms & Signs of Cancer in Cats

Effects of Cancer – From the Cat’s Point of View

Our feline friends may not look much like us, but mammals are mammals and cats can suffer from many of the same diseases and other medical conditions that affect people. Unfortunately, cancer is one of them.

Cancer is more common in cats than in dogs or other companion animals. It tends to affect middle-aged and older cats most frequently, and also those that have not been spayed or neutered.

One exception to this is lymphoma (also called lymphosarcoma), which typically is seen most often in younger cats. Regardless of their age, cats that are infected with the feline leukemia virus (FeLV) or the feline immunodeficiency virus (FIV) have a heightened risk of getting cancer.

While they can develop a number of different kinds of cancer, there are several types that seem to affect cats most frequently. These are lymphoma, skin cancer, breast cancer and squamous cell carcinoma of the mouth.

Feelings of a cat with cancer, depends on how advanced its condition is and which of its organs are affected. Most cats don’t show any signs of pain, discomfort or distress in the early stages of cancer.

However, as the disease progresses, metastasizes (spreads) and starts invading the lungs, kidneys or other vital organs, the animal will become increasingly ill. Cats with late-term or end-stage cancer usually lose their appetite, drop weight, become nauseous and are reluctant to move around or exercise.

Symptoms of Cancer – What the Owner Sees

Owners of cats that have cancerous lesions in their mouth, which almost always involve malignant squamous cell carcinoma, often notice one or more of the following signs:

  • Excessive drooling (ptyalism)
  • Lumps or bumps on the gums, inner cheeks and/or tongue; these often are ulcerated, oozing and bloody
  • Difficulty eating, chewing and swallowing
  • Reluctance to eat or drink
  • Weight loss
  • Bad breath (halitosis)
  • Lethargy

Cats with cancer in their gastrointestinal tract may develop one or more of the following symptoms:

  • Abdominal pain
  • Difficulty eating
  • Vomiting
  • Diarrhea
  • Constipation
  • Bloody stools
  • Straining to defecate (tenesmus)
  • Poor body and coat condition

Female cats that have cancer in their reproductive tract may have vaginal bleeding or other abnormal vaginal discharge. Bone cancer, which is uncommon in cats, can cause swelling and pain at the tumor site and intermittent lameness if it involves bones of the legs.

Although primary lung cancer is also rare in domestic cats, other types of cancer often spread to the lungs. Owners of cats with secondary lung tumors may observe one or more of the following signs:

  • Difficulty breathing (dyspnea)
  • Coughing
  • Wheezing or other abnormal breathing sounds
  • Weakness
  • Lethargy
  • General malaise and ill thrift

Cats at Increased Risk of Cancer

Aging cats and intact cats have an elevated chance of developing cancer, as do those infected with the feline leukemia virus or the feline immunodeficiency virus. Cats exposed to secondhand smoke, radiation and certain chemicals may also be at increased risk.

How Cancer in Cats is Diagnosed

Initial Evaluation

Many cases of cancer are discovered when a cat’s owner or veterinarian feels or sees a lump or bump somewhere on or inside of the cat’s body. Visible skin masses can occur anywhere on a cat’s body but most often show up on the face, nose, lips, mouth (gums and tongue), head, ear tips, back of the torso and/or legs.

The most common internal tumors that can be felt (palpated) are those that involve lymph nodes located either under the cat’s front “armpits” or in the groin area near the inner thighs of its hind legs.

The other way that cancer is often detected is when a cat is taken to the veterinarian because of a slow, steady decline in its overall health, body condition and energy level, for no apparent reason.

Diagnostic Procedures

A veterinarian who sees a cat with obvious abnormal masses will probably recommend taking a biopsy sample to see what the lump is made of. In many if not most cases, the veterinarian will remove the entire mass rather than only just part of it, trying to get clean surgical margins of healthy tissue all the way around the tumor.

The removed tissue will be sent to a laboratory for evaluation by a skilled veterinary pathologist. Sometimes, the doctor will take a sample of the mass using a technique called a fine needle aspirate, or FNA.

This involves sticking a sterile needle into the lump and drawing cells and fluid into an attached syringe. The sample will be expressed onto a sterile glass slide and assessed under a microscope.

If the cat doesn’t have obvious superficial lumps or enlarged lymph nodes but is just not feeling or acting well, the veterinarian will take blood and urine samples to check how the animal’s key organs are functioning.

She probably will also run blood tests for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV). These are relatively simple and inexpensive tests that can be performed at any local veterinary clinic.

Radiographs (X-rays) of a cat’s chest are helpful to determine whether any type of cancer has spread to the lungs. If the cat is limping or has painful swollen joints, radiographs can help identify bony abnormalities.

Advanced imaging techniques, such as ultrasound, magnetic resonance imaging (MRI) and computerized axial tomography (CAT) scans, are available at veterinary teaching hospitals and some specialized private veterinary practices. These can be used to identify internal masses.

The results of these diagnostic procedures will guide the medical team’s treatment suggestions and protocols. The laboratory report from the pathology laboratory evaluating biopsy samples is probably the single-most important piece of diagnostic information.

Treatment of Cancer in Cats

Goals of Treating Cancer in Cats

While a diagnosis of cancer is never good, early detection and treatment of cancer in cats can be remarkably successful. Surgery is usually the treatment of choice, although some types of feline cancer respond better to radiation, biological, chemical or heat-related therapies.

Sometimes, the recommended approach is to use a combination of treatments. The primary goal of treating cancer is to eliminate all cancerous cells from the cat’s body. If that isn’t possible, the goal is to put the cancer into remission and make the animal as healthy and comfortable as possible, for as long as possible.

Surgical Treatment Options

Solitary cancerous masses are usually removed surgically. It is extremely important for the veterinarian to excise a wide margin of normal tissue around the tumor. This is called “getting clean margins.” Incomplete removal of cancerous tissue almost always causes the cancer to return, making it increasingly difficult to treat.

Sometimes, it may be appropriate to remove masses even if clean margins aren’t possible, such as when the tumors are infected or physically interfere with the cat’s normal activities.

The veterinarian will submit all removed tissues to a laboratory, where pathologists will determine the type of cancer involved and whether clean surgical margins were obtained. This information will guide the course of further treatment.

Non-Surgical Treatment Options

If a cat’s tumors are inoperable, other treatment options are available. These include radiation, chemotherapy, heat-based therapy and immunological therapy, among others.

Many cancer cells are killed by exposure to high levels of radiation, although radiation can also kill healthy tissue, which is one of its adverse side effects. Chemotherapy involves giving anti-cancer drugs that target and destroy rapidly-dividing cells throughout the cat’s body, including cancer cells.

Unfortunately, cancer cells aren’t the only ones that multiply rapidly. Other cells that do this are hair cells and those lining the gastrointestinal tract, which explains why hair falls out and patients often become nauseous when receiving chemotherapeutic treatment.

While the goal is to eliminate all cancer cells, it isn’t presently possible to completely isolate healthy tissue from cancerous tissue during these treatments. Sometimes, the veterinarian will recommend multiple therapies, such as combining surgery with radiation or chemotherapy.

Heat-based therapies, such as electrocautery and cryosurgery, can be used to remove tumors on a cat’s skin, depending on their size and location. Electrocautery, also called hyperthermy, involves using heat to burn off skin tumors.

Cryotherapy involves freezing off cancerous skin masses. Hormone therapy and immunotherapy can help manage some types of cancer. An emerging treatment uses special drugs that are sensitive to particular wavelengths of light.

These are injected into the cat together with a substance that targets cancer cells. The tumor is then saturated with light. Like most other cancer treatments, these newer procedures are only available at highly specialized veterinary referral centers.

Supportive Cancer Therapies

Modern cancer management involves far more than surgery, radiation or chemotherapy. Nutritional support, pain management, ulcer prevention, physical therapy and other supportive techniques are all critical components of a comprehensive cancer treatment plan.

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