Nobody likes to hear the “Big C” word. Unfortunately, some cats do get cancers. Learning about cancer helps prepare a family to deal with diagnosis and treatment of their cat.
Cancer is much more likely to develop in a cat that has reached her golden years, but even young cats can develop this condition. Cancer is not just one entity—it is any process of uncontrolled cell growth. Cancer can affect all cell types, and thus any organ system, or a number of systems at once. Cancers behave in very different ways depending on the nature of the tumor. The word “tumor” just describes a lump; an overgrowth of cells, and does not describe the behavior of those cells.
Cancerous tumors are lumps that are abnormal, and are classified into benign and malignant depending on their behavior. Some cancers grow very slowly and predictably. These are often well encapsulated so that they can be easily removed with surgery or freezing, and do not spread around the body. We refer to these as benign tumors.
Others act like a wildfire, growing quickly, spreading throughout the body to distant locations, and may lead to a quick demise of the unfortunate animal. These aggressive cancers we term malignant tumors. These tumors often have tendrils of microscopic cancer cells that extend along tissue planes quite a distance from the main lump and thus cannot easily be removed by surgery. Other cancers affect cells of the bone marrow and bloodstream, and thus are present in the blood as it circulates. This is typical of the leukemias. Sometimes a single tumor seeds via the bloodstream into multiple locations. Frequently seeding occurs in the lungs.
External cancers that can be felt or seen on the surface of the cat are much easier to pick up than the internal cancers. Home monitoring on a regular basis for unusual lumps and bumps can help a cat owner be a first line sentinel to identify new growths. Any new bumps should be brought to the attention of the veterinarian because felines have a high proportion of cancerous lumps.
Signs of internal cancers are tougher to check for at home. No signs may be present. Other times, vague signs of reduced appetite, weight loss and muscle wasting, reduced energy, vomiting, diarrhea, pale membranes, difficult breathing, or trouble moving around may occur. Signs tend to correlate with the system affected, so only a small subset of signs may be present.
Diagnosis of cancer typically involves carrying out blood tests, imaging studies, and a biopsy.
Advanced imaging is more widely available these days. The CT scans, MRI, and endoscopy give us a much better look into tissues than was possible even a few decades ago. Specific biomarker tests are still rare, but research into tumor markers in cats continues. Specific staining techniques of the biopsy tissue can help the pathologist make a very detailed analysis of the cellular nature of the tumor, and this has helped veterinarians improve treatment, and provide more accurate assessment of prognosis. Cancer is staged as with people so that we can determine at what point along the spectrum of disease progression a particular patient sits. This helps the clinician counsel the owner regarding optimal treatment plans.
Certain risk factors make cats more likely to develop cancers. Cats with white on ears and nose are more prone to developing squamous cell carcinoma, a cancer of the skin. Cats that have chronic virus disease such as Feline Leukemia Virus are more prone to lymphomas, fibrosarcomas, and other cancers. Certain breeds are predisposed to mediastinal lymphosarcoma such as the Oriental and Siamese breeds. The Abyssinian and Somali breeds can develop a rare thymoma-associated neuromuscular disorder. Cats that are spayed as adults have increased prevalence of mammary tumors.
Early diagnosis is important for the outcome. Treatment options may include radiation, surgery, chemotherapy, immunotherapy, cryotherapy, or palliation and nursing care. Intervention with an early, well designed therapy strategy allows many cats to enjoy an extended lifespan with an acceptable quality of life, and in some cases, cancer treatment can be curative.