The 10 Most Dangerous Types of Cats Cancers

Sick Cat

Cats are friendly and cute pets that make beloved family members. Sadly, when your cat is diagnosed with cancer, it can be very devastating. Research statistics show that more than six million cats are diagnosed with cancer annually. But similar to humans, some cancers are more dangerous than others. This said, understanding the aggressive and dangerous types of cancer in cats and how to spot the signs is an important part of being a proactive cat owner. Here is an exclusive review of the 10 most dangerous types of cat cancers.

10. Bone Cancer (Osteosarcoma)

Osteosarcoma is a type of malignant cancer that arises from bone cells. This type of cancer is often painful and can cause limb swelling, bone fractures, and lameness. The signs of bone cancer in cats include swelling, lameness, and lethargy. Although rare, bone cancer tends to be very aggressive and dangerous. Bone cancer tends to spread rapidly throughout the body.

The tumors can spread to the adjacent sites, such as multiple myeloma of the bone marrow or the metastatic lesions from the distant tumor site. According to current studies, there is no evidence showing why cats develop this cancer, although it is more common in giant and large breed cats. Bone cancer is often difficult to treat and has many side effects. If you have a large cat breed that suddenly becomes lame for no clear reason, consider taking it to the veterinarian for bone cancer diagnosis right away.

9. Lymphoma

Lymphoma is one of the most common and dangerous types of cat cancer. This is a type of blood cancer that happens when lymphocytes multiply uncontrollably. Lymphocytes refer to white blood cells that protect the body from infections. In cats, lymphoma normally affects the lymph nodes, nasal cavity, intestines, liver, and kidneys, which contain lymphoid tissue. According to AVIM&O, cats of any breed, age, and sex can be affected by lymphoma. Feline leukemia virus (FeLV) was the most common cause of lymphoma in cats before the development of the FeLV vaccine.

Cats with the feline immunodeficiency virus (FIV) also have an increased risk of developing lymphoma. This vaccine has played a great role in protecting cats against FeLV and indirectly protecting them against particular forms of lymphoma. Lymphoma is aggressive but often responsive to chemotherapy when diagnosed early. Around 70% of cats get remission. However, other side effects may include vomiting, nausea, diarrhea, infection, or tiredness. Cats may not lose their hair but might get a different fur texture or lose their whiskers.

8. Squamous Cell Carcinoma

Squamous cell carcinoma arises from the cells lining the oral cavity. This squamous cell carcinoma is a form of skin cancer that accounts for a high percentage of all cat skin tumors. These tumors normally involve unpigmented or light skin with sun exposure increasing the risk of a cat developing squamous cell carcinoma. The common areas are the hairless area of the mouth, eyelids, nose, and ears. Most cats with oral squamous cell carcinoma often display foul odor, drooling, difficulty eating, or bleeding from the mouth. Some cats might show symptoms signifying a dental issue, and squamous cell carcinoma is diagnosed as an underlying cause of dental disease. According to Flint Animal Cancer Center, if your cat develops sores on the skin that will not heal, this could be a sign of skin cancer.

For the treatment of this type of feline cancer, surgery is the first option wherever possible. However, curative surgery is only possible for less than ten percent because of the small size of a cat’s mouth and the large size of the tumor during the diagnosis. Surgery is an option that normally involves removing the parts of the lower or upper jaw due to the tumor’s ability to attack bone and other deeper mouthparts. Chemotherapy and radiation offer extra treatment options. Unfortunately, only a few cats with squamous cell carcinoma can be cured. The treatment goal is to maintain an excellent quality of life. But if you notice it on time, you and your cat can beat the nasty disease together.

7. Injection-site sarcoma

An injection-site sarcoma is a tumor that affects the connective tissues in the cat. The common cell type affected by injection-site sarcoma is the fibroblast, making the tumor referred to as fibrosarcoma. Other types of tumors described include; chondrosarcoma, osteosarcoma, and malignant fibrous histiocytoma. These tumors have the same behavior and are hence often treated in the same way. Injection-site sarcoma is often situated between the shoulder blades in the back legs and the hip region. According to UCHealth, the spread of the tumors to other body parts is around 25%.

The effect relationship and cause of injection-site sarcoma have been established for particular vaccines, including feline leukemia and rabies. Other chronic injections such as lufenuron have also been found to cause the tumors. There is a possibility that the development of the tumors in certain cats is linked to genetic predisposition. However, the exact genetic issue is yet to be identified. As one of the most dangerous cat cancers, injection-site sarcomas are difficult to treat.

Cats with tumors on the legs where they can get amputated seem to do better than cats with tumors on the trunk. However, combining chemotherapy, surgery, and radiation therapy relatively increases the tumor-free time to around one or two years. Felines with tumors reoccurring after repeated surgeries before other treatments are tried are more challenging to control. Therefore, the first time it occurs is the best time to treat the tumor with radiation therapy and chemotherapy.

6. Lung Cancer

Lung cancer in cats is one of the most dangerous. This cancer can affect any cat breed, although Persian cats have a higher diagnosis rate. Unfortunately, there is no specific answer on what causes this cancer as it can result from a mix of genetic and environmental risk factors. However, age is also a significant factor. According to research, most primary lung tumors are diagnosed in older cats, with an average age of twelve. According to Pet Cure Oncology, exposure to environmental carcinogens like cigarette smoke has been linked to lung tumor development. But in terms of sex, it doesn’t seem to affect a cat’s risk of developing lung cancer.

Noticing the signs of lung cancer can be challenging because many cats don’t show any symptoms in the early stages of cancer. However, there are a few signs of general illness, such as lethargy, poor appetite, weight loss, and regurgitation. Coughing can also occur, although it is uncommon in cats with lung cancer, particularly in the early stages of the disease. Lung cancer prognosis in cats depends on the type of tumor and the cat’s treatment response. The cat can survive for several months to two years with successful surgical removal of the primary tumor and no metastasis signs.

5. Brain Cancer (meningioma)

This type of cancer is not widespread, but it is often severe if your cat gets it. Brain cancer is more common in male than female cats. Meningiomas refer to primary brain tumors that account for around 56 to 65% of cats’ brain tumor types. Other brain tumors include gliomas, pituitary tumors, choroid plexus papilloma, ependymoma, olfactory neuroblastoma, medulloblastoma, and gangliocytoma. The clinical symptoms of brain cancer include seizures, mental dullness, and difficulty walking or walking in circles. Radiation therapy often reduces the lesions for around a year or two.

4. Mammary Tumors

Mammary or breast cancer is common in cats representing the third most common type of cat cancer. These are tumors that occur from the breast or mammary tissues of cats. According to PET MD, cats have two rows of mammary glands with four in every chain running the length of a cat’s belly, meaning tumors can develop anywhere from the groin to the armpit. The tumors can originate in the mammary gland but can spread to the adrenal gland, lymph nodes, liver pleura, lungs, and kidneys.

About 90% of mammary tumors in cats are malignant. This means that they have the potential to spread to other body parts. On the other hand, about ten percent of mammary tumors are benign, meaning they won’t spread to other regions. However, the determination of whether the mammary tumors are benign or malignant is only made by a specialist pathologist after removal. The most effective therapy for mammary tumors is surgical removal at the earliest chance.

A complete surgical excision might be curative if the tumor is in the early stages. Post-surgical treatment with chemotherapy is recommendable for bigger tumors or when the lymph nodes are involved. Important to note that cats spayed before six months of age are more likely not to develop mammary tumors than those spayed after six months.

3. Fibrosarcoma

Fibrosarcoma is another type of cancer seen in cats. This aggressive and dangerous tumor develops from the fibrous connective soft tissue. This type of tumor spreads slowly to other body parts but is locally aggressive. Cat owners will normally notice a skin mass that does not cause discomfort or pain. When the cancer is more advanced, the cats become lethargic, dehydrated, or anorexic. Fibrosarcoma has developed at injection sites of several necessary preventives and medications, where it is known as the feline injection-site sarcoma (FISS). It’s mostly linked with antibiotics, vaccines, corticosteroids, subcutaneous fluids, and insulin injections. In many cases, fibrosarcoma treatment starts with surgery. However, the tumor often recurs even with aggressive surgery. Chemotherapy or radiation is hence often recommended as an adjunctive treatment.

2. Mastocytomas

Commonly known as mast cell tumor, this is a cancer of the cat’s skin. Mast cells are a certain type of normal white blood cells and can often become tumorous. Mast cell tumors often occur in a cat’s skin but also affect the liver, lungs, spleen, and intestinal tract. Cat owners might notice an abnormal patch or lump of the skin, which can be itchy. The internal forms of cancer are commonly linked with poor appetite, weight loss, diarrhea, or vomiting. Cats of any age can be affected by this cancer. For the diagnosis of mast cell tumors, veterinarians mostly use a microscope to view the cell samples derived from the tumor.

They might also recommend conducting a biopsy with the pathologist to get more details. Their prognosis is great if a cat is diagnosed with only a few mast cell tumors that can be fully removed through surgery. Removing a cat’s spleen will often provide cats with a year of good life quality if that is where their tumor is situated. Antihistamines are also often prescribed for digestive problems until cancer gets under control. Felines with intestinal mast cell tumors often have the poorest prognosis as this form of cancer tumor spreads fast. According to, any cat can be diagnosed with mast cell tumor, but Siamese is more susceptible.

1. Hemangiosarcoma

Hemangiosarcoma is one of the most dangerous tumors in cats. It is a highly malignant cancer that spreads rapidly, causing tumors almost in all body parts. This type of cancer involves tumor cells lining the blood vessels but most often affects the spleen, heart, skin, or liver. It can spread quickly but, in some cases, might go unobserved until it’s too late. Hemangiosarcoma results in a bump on the skin surface after the internal organs have been affected. If you see a lump on your cat’s body, consider taking it for a biopsy to establish whether it’s a benign or malignant tumor. If the veterinarian diagnoses it as hemangiosarcoma cancer, he will decide on whether to remove it through chemotherapy if it’s widespread or through surgery if it’s on the cat’s spleen.

Bottom Line

These are the ten most dangerous types of cancers. The good news is that with treatment, many cats can continue living quality lives after a cancer diagnosis. Engaging in practices that help decrease the risks of cat cancer is important, such as exercise, a good diet, avoidance of cigarette smoke, and low stress. As a cat owner, it’s recommendable to keep safe and consult any new symptoms with your veterinarian. Early intervention is often the key to treating cancer in cats effectively and enhancing their life quality.

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