Types of Cancer in Cats

Dog Breeds

Cats can develop a lot of harmful medical conditions that people have as well. Sadly cancer is one of these conditions, and cancer is one of the leading causes of death in cats. Cats can develop any number of types of cancer, but there are two cancers that cats are most often diagnosed with: lymphoma and skin tumors.

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Introduction

Our feline friends may not look like us, but mammals are mammals, and cats suffer from some of the same diseases and medical conditions that affect people. Unfortunately, cancer is one of them and is one of the leading causes of feline death. The increasing number of diagnosed cancer cases in cats is probably due largely to the fact that cats are living longer with our significant improvements in companion animal nutrition and overall health care. Nonetheless, any prominent or persistent mass should be evaluated for malignancy.

Common Types of Cancer in Cats

The most common types of feline neoplasia are lymphoma, mammary cancer, basal and squamous cell carcinoma, mast cell tumors and fibrosarcoma.

Feline Lymphoma

Lymphoma is a general term applied to the system-wide and malignant neoplastic transformation of lymphoid tissue. It is the most commonly treated systemic cancer in veterinary medicine and is the most common hematopoietic malignancy in cats (“hematopoietic” means pertaining to or affecting the formation of blood cells). Lymphoma is very aggressive and frequently affects multiple lymph nodes, the spleen, liver, gastrointestinal (alimentary) tract and/or bone marrow. The symptoms of feline lymphoma depend upon what type of lymphoma the cat has and the particular organs affected. If diagnosed and treated early, lymphoma normally can be well-managed. Many cats achieve complete remission following chemotherapy. Without treatment, however, the prognosis is very poor. Feline lymphoma is seen more often with cats that are infected with the feline leukemia virus (FeLV) or the feline immunodeficiency virus (FIV). It also is more common in house cats exposed to chronic environmental tobacco smoke.

Feline Mammary Neoplasia

Tumors of the mammary glands are common in intact female dogs but less so in cats. Still, they represent the 3rd most common tumor type in cats. They most frequently affect older intact queens; Siamese cats are reported to have twice the risk of developing mammary cancer as all other cat breeds combined. Most of these tumors are adenocarcinomas that tend to present on the anterior (front) rather than the posterior mammary glands. In cats, approximately 90% of mammary masses are malignant and require aggressive surgical removal. The outlook for cats with mammary cancer is usually guarded, and depends largely upon how early the cancer is diagnosed and the success of aggressive treatment.

Skin and Subcutaneous Cancer in Cats

Soft tissue sarcomas are a group of tumors which arise from connective tissue and are classified together because of their similar biologic behavior and recommended treatment protocols. Feline skin tumors can be caused by a number of neoplastic processes. The most common forms of skin cancer in cats are basal cell carcinoma, squamous cell carcinoma, mast cell tumors and fibrosarcoma. Depending upon the cause of the mass, it may be small or large, soft or firm, grow quickly or slowly, be above or beneath the skin and be solitary or clustered with other masses. Many skin tumors metastasize if not promptly removed. These tumors are more common in middle-aged to older cats, and no evidence of direct genetic inheritance has been reported at the time of this article. Soft tissue sarcomas tend to show up spontaneously in cats and appear as firm masses on the legs, mouth or chest often appearing to be on top of, or right under, the skin. The goal of treating soft tissue sarcomas is complete eradication and removal.

Basal Cell Carcinoma

Basal cell tumors typically are solitary nodules that are frequently pigmented and occasionally ulcerated in cats. While usually localized on dogs, basal cell tumors can be found almost anywhere on cats. They are the most common type of feline skin tumor. Most feline basal cell tumors are benign, but when they are definitively diagnosed as carcinoma, they should be removed swiftly and aggressively, with wide surgical margins.

Squamous Cell Carcinoma

Squamous cell carcinomas frequently present as ulcerated, non-healing, crusty, weeping and necrotic sores. In cats, they tend to show up on the ear tips, lips, nose, oral cavity and eyelids and are the most common feline tumor in these areas. They can be exacerbated by exposure to ultraviolet light, especially in white or very lightly pigmented cats with pink skin. Complete surgical excision is the treatment of choice, with radiation if surgical margins are incomplete. Chemotherapy is also an option.

Mast Cell Tumors

Mast cell tumors (MCTs) are fairly common in cats, representing about 20% of all feline skin neoplasms. Siamese cats under 4 years of age have a higher incidence of mast cell tumors than do other feline breeds. These tumors are abnormal accumulations of mast cells that form nodular tumors which, when the mast cells degenerate, release histamine and other irritating substances that can cause or contribute to gastrointestinal ulceration, cutaneous lesions (including itchiness) and systemic clinical signs. Mast cell tumors have the potential to become malignant and metastasize to other sites. Therefore, they should always be treated immediately when diagnosed. Treatment options include surgery, radiation, chemotherapy and immunosuppressive steroid administration. The appropriate treatment protocol will depend upon the diagnostic stage of the tumor(s) and the veterinarian’s particular recommendations.

Fibrosarcoma

Fibrosarcoma typically originates in subcutaneous connective tissue. In cats, this tumor is more common in association with feline leukemia virus, feline immunodeficiency virus and as vaccine-site-associated reactions. Fibrosarcoma tends to show up as solitary tumors on the head, in the mouth, on the trunk or on the legs. For some reason, there is a strong association between certain inactivated feline vaccines and development of soft tissue fibrosarcomas at the injection site. Fortunately, injection site fibrosarcomas are not common in cats. Unfortunately, feline fibrosarcomas can be extremely invasive and aggressive. While surgical removal is possible, without wide and clean surgical margins the masses often return. The potential for vaccine-associated fibrosarcomas should not deter owners from vaccinating their cats. Oral fibrosarcomas are the second most common oral malignancy in cats (second only to squamous cell carcinoma) and are highly invasive into surrounding bone.

Treatment Options

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