Explaining Lymphosarcoma in a young cat
By Bernard Pukay DVM
October 15, 2013
Question: Two years ago, our family adopted a three-month-old cat. Its mother had been found on the streets and he was born at the Humane Society. He had been sterilized and received a microchip implant. We promptly took him to a veterinarian, who examined him and gave him his mandatory vaccines.
He was a healthy cat and only returned to the veterinarian annually for checkups. He was fed exclusively with a proper cat food and as much water as he wanted, and his litter box was thoroughly cleaned once daily.
Last summer, after having turned two years old, his appetite suddenly declined significantly and we took him to the veterinarian. He was diagnosed with lymphatic cancer and his doctor recommended putting him down during exploratory surgery when nothing else could be done to save him.
We see no possible cause for such a very young healthy cat to die in this way other than some genetic unknown factor. Nevertheless, we cannot help thinking that cat owners would benefit from any research on such diseases, on any known carcinogenic factors and any advice veterinary science could provide us, so that we can do our best to prevent similar premature deaths.
Answer: Unfortunately, your cat came down with the most common type of feline cancer, also known as malignant lymphoma or lymphosarcoma. This form of cancer originates from lymphocytes in the blood and can affect several different parts of the body including the intestines, the mediastinum (the middle section of the chest), lymph nodes, kidneys, spine, skin and even the eyes or nose. It can develop at any age, including young cats such as yours.
The feline leukemia virus (FeLV) and the immunodeficiency virus (FIV) are considered to be risk factors for the development of lymphoma. Cats with either of these infections have a significantly increased risk of getting lymphomas compared to the general population.
Chronic exposure to “second-hand” tobacco smoke also increases the risk. In one study, cats exposed to long-term tobacco smoke had a 2.4-fold increased risk of getting lymphoma.
Approximately seven per cent of the general cat population is infected with FeLV and cats become infected via direct contact with infected saliva, either through mutual grooming (e.g. open wounds or sores) or bite. The incidence is highest in stray cats because they tend to encounter more cats and get into more fights than owned indoor cats.
Not all cats that are exposed to the FeLV virus necessarily become infected. Young cats tend to be more susceptible than older cats. It is possible that your cat picked up this virus from its mother at the shelter and was infected with it from the start.
When natural exposure to the FeLV virus occurs, one of three things can happen: (1) the exposed cat may not become infected at all (e.g. because of exposure to only a low dose of virus or because of natural resistance), (2) it may become infected temporarily, or (3) the exposed cat can become infected and eventually die. Cats in this last category are typically young cats and they usually die within three to four years of exposure as a result of FeLV-related disorders such as lymphatic cancer. Only in rare cases do they manage to live longer.
There are a few things that can be done to minimize the risk of a cat getting lymphatic cancer. Cat owners can make sure that risk factors are kept to a minimum or avoided. Keeping a cat from roaming outdoors and eliminating exposure to “second-hand” tobacco smoke are two important preventive measures.
Similarly, in cats at risk (i.e. a stray or an outdoor cat), vaccinating with FeLV and FIV vaccines is recommended. Monitoring for FeLV and FIV by means of regular blood testing for the presence of these viruses can lead to early detection of a FeLV or FIV infection and possibly allow for early treatment with chemotherapy. Testing is especially important when introducing a new or stray cat into a multi-cat household.