Types of Cancer in Cats
As with humans, cats can get cancer in a very large number of body organs. Here we describe some of the more common cancers, the prognosis (how the disease is likely to progress) and treatments.
Lymphoma and leukaemia
Leukaemia is a cancer of the white blood cells. Lymphoma is a tumour of the lymph nodes. Lymphoma affects cells known as lymphocytes and is probably the single most common cancer that affects cats. Lymphocytes are important in the body's defence against disease. They are found in many tissues but mainly in lymph nodes. Lymphocytes circulate through the blood and lymphatic system and therefore it is very easy for cancerous cells to spread. In lymphoma, cells in the lymphatic system grow abnormally. They divide too rapidly and grow without any order or control. Too much tissue is formed and tumors begin to grow. The liver, bone marrow and the spleen are also frequently affected.
Treatment for lymphoma varies depending on where the tumour is and how far it has grpwn or spread. Cats usually stand up well to chemotherapy. Most cats will not lose their hair from the treatment, though the hair may well go white. The results of chemotherapy on cats are good and long lasting, although it is rare for the tumour to be completely eliminated.
The prevalence of skin cancers in cats varies considerably depending on the environment. Cats in areas with long periods of harsh sunlight are more vulnerable, but other factors, such as exposure to toxic waste also play a part. It is important to note that not all the skin and subcutaneous tumours which a cat may develop are malignant. Around 35-45% of these tumours may be benign - that is, not harmful or life-threatening. There are many tumours which affect the skin and subcutaneous tissue. The names of the most common malignant types are: Basal Cell Tumor, Mast Cell Tumor, Squamous Cell Carcinoma, Fibrosarcoma, Adenocarcinoma.
Skin cancers are equally common among cats of both sexes, and tend to become more common with age. Squamous Cell Carcinoma is particularly prevalent in white cats. This is especially the case if the cat is an outdoor cat which has had prolonged exposure to sunlight. Squamous cells are thin, flat cells resembling fish scales (the name is Latin for 'scales'). Squamous Cell Carcinoma is generally found on the cat's nose or the ears, and it can initially look like a small scratch or wound that won't heal. If caught early, the tumour can usually be removed successfully by surgery, followed up with radiation treatment.
Squamous cell carcinoma is a tumour effecting squamous epithelial cells. These are found not only on the surface of the skin, but in the lining of the hollow organs of the body, and the respiratory and digestive tracts. In the mouth the tumour usually affects the lining of the mouth or the lining of the throat, but it also affect the tongue. You may notice a cat has oral cancer when it has difficulty in eating, or if it drools continuously. Oral cancers are difficult to treat, but some success can be achieved by surgery combined with radiotherapy.
Adenocarcinoma, or Sweat Gland Neoplasm, is a cancer that develops in the lining or inner surface of an organ. It is relatively common in cats, making up approximately 13 percent of all skin tumours which cats develop. Most sweat gland tumours occur on the head and neck. The treatment of choice is surgical removal. Adenocarcinoma is also common in lung cancer and intestinal cancer (see below).
A number of tumours can cause lung cancer in cats, the most common being adenocarcinoma. Adenocarcinoma can cause difficulty in breathing, coughing, or a mixture of the two symptoms. Sometimes the cancer spreads to the bones in the cat's toes and causes lameness. Surgery is the treatment of first choice, usually combined with chemotherapy. How the disease progresses depends on how early the tumour caught. Often by the time the symptoms become apparent, the tumour has gone deep into the lungs and may well have spread into the chest cavity. In that case the prognosis is poor.
Again ademocarcinoma is the problem. It can effect both the small and large intestines. It is also common for the tumour to spread to the local lymph nodes. Tumours can grow quite fast and are often discovered because they end up by blocking the intestines. The typical symptoms are: loss of appetite, weight loss, vomiting and diarrhoea. Surgery is relatively quick and simple and can bring long-lasting relief.
Mast cell tumours
As the name says, mast cell tumours affect mast cells. These are cells which are found in connective tissue, the layer of cells between different body parts (for example between the heart and lungs). mast cell tumours in the skin manifest themselves as nodules or as single large lumps which can be removed by surgery. However, because mast cells are not only found in the skin, your vet will want to check other parts of the cat's body, including the liver, lymph nodes, bone marrow, intestines and spleen. When a mast cell tumour is found in the spleen, removing the spleen can result in a disease-free life for up to 12 months.
Cats (both male and female) have four breasts on each side of the tummy, visible as two rows of nipples. Tumours may occur in one or more of these breasts, though the disease is much more common in female cats, as their breasts are more developed. The tumour commonly affects more than one of the mammary glands. These tumours can be felt in the cat's breast as multiple firm swellings or nodules. Early diagnosis is important, as eighty percent of these tumours usually turn out to be malignant cancers. If not caught early, these can go on to become dangerously large swellings and the cancer can spread to the lungs and lymph nodes. The treatment will then require additional chemotherapy. in dealing with breast cancer, the surgeon will probably remove all the breast tissue on the affected side, since if only the present lumps are removed, there is a high chance that further tumours will develop.
Fibrosarcoma is a tumour affecting fibroblasts (fibroblasts are cells which are the building blocks of the connective tissue). The most common tumour affects the skin, producing a hard subcutaneous mass. The treatment involves a combination of surgery and radiotherapy or chemotherapy.
This are relatively rare in cats, constituting only 5% of primary cancers. Osteosarcoma is the most common feline bone tumour, being responsible for approximately 70% of all bone tunours discovered. It mostly affects the bones in the legs, but it can establish itself in any bone including those of the spine. If a leg is affected, the vet may choose to amputate it. Incredibly, cats often adapt well to life with three legs, and there are cases of even feral three-legged cats living long lives and raising kittens in the process. If amputation is unsuitable for any reason, radiation and chemotherapy may also be used.
Note: This information is for guidance only. It is not intended to replace consultation with a licensed practitioner.