Feline cancer can take many forms. Cancer cells are normal cells that,
for a variety of reasons, grow abnormally. 
Some feline cancers are
benign, meaning they growths do not invade other cells. Other feline cancers are
malignant, and the cancerous cells begin to attack other healthy cells. As cats
and other pets live longer, cancers are becoming more common. While cancer can
begin anywhere in the body, most feline cancers affect the liver and lungs most
severely. The cancer may begin in these organs or begin elsewhere and spread, or
metastasize, to the liver or lungs.
Causes of feline cancer are often unknown. Some forms of cancerous tumors may be genetic in nature. Others are likely caused by environmental factors to which the cat has been exposed. Still other feline cancers may be caused by viruses. Feline cancer can occur in cats of any age.
Common signs of feline cancer can include the following:
- Abnormal swellings that grow or persist
- Loss of appetite
- Persistent stiffness or lameness
- Bleeding or discharge from any body opening
- Weight loss
- Sores that do not heal
- Difficulty eating or swallowing
- Difficulty breathing, urinating, or defecating
- Offensive odor
- Loss of stamina or lethargy
Some common forms of feline cancer include lymphoma, squamous cell carcinoma, mammary carcinoma, mast cell tumors, oral squamous cell carcinoma, fibro sarcoma (also known as soft tissue sarcoma), osteo sarcoma, respiratory carcinoma, intestinal Aden carcinoma, and pancreatic and liver Aden carcinoma.
Depending on the type of cancer and the stage at which it is diagnosed, some feline cancers are very treatable. Chemotherapy is often recommended as a treatment for feline cancer. While the treatment carries risks and may cause side effects (the most common of which is loss of whiskers), many cats respond well to chemotherapy.
