What is a lymphoma?
Lymphomas are cancers of the lymphocytes, a type of immune cell. Although in dogs they generally arise from the lymph nodes, they generally involve other organs in cats. The most common locations in cats are the gastrointestinal tract, the kidneys, the nose, and the chest (mediastinum). As immune cells are made to travel within the body to fight against infection, lymphomas often inherit from this trait and can easily spread throughout the body. More commonly than in dogs, lymphomas in cats can remain local, however.
What are the different types of lymphomas?
The most important way caracterise lymphomas in cats is to determine where it started from. As mentioned above, feline lymphomas are best characterised as gastrointestinal lymphomas, renal lymphomas, mediastinal lymphomas, nasal lymphomas and nodal lymphomas. Gastrointestinal lymphomas represent 40% to 50% of all cases, you can find out more information about it here.
Some lymphomas will progress very slowly (indolent / low grade), whilst the majority will progress quickly (aggressive / high grade). The most common lymphoma in cats is the low-grade gastrointestinal lymphoma, and cats may also occasionally develop low-grade lymphomas in other places such as the lymph nodes (so called Hodgkin’s like lymphoma). Many lymphomas will exhibit an aggressive behaviour, however.
How can I tell if my cat has lymphoma?
Clinical signs are very variable and largely depends on where the lymphoma started. Cats with gastrointestinal lymphomas may develop diarrhoea, vomiting, decreased appetite or simply weight loss. Lymphomas within the nose may trigger sneezing, discharge and eventually a bump/asymmetry of the head may develop. Shallow and rapid breathing can be noted with chest lymphomas and an enlarged lymph node (lump within the neck) can also be palpated in some cases.
What causes lymphoma?
In most cases, we do not know exactly what causes lymphoma, and it is likely that genetic and environmental factors play a role. In a few studies, some breeds have been reported to predisposed, including Siamese and Oriental breeds. Some viruses, including Feline Immunodeficiency Virus (FIV) and Feline Leukaemia Virus (FeLV), can also favour the development of lymphomas. Although most feline lymphomas were associated with FeLV before the 1980s, mass testing, quarantine and vaccination programs dramatically reduced the incidence of these viruses. Exposure to tobacco smoke may also increase the risk of developing lymphoma in cats.
How are lymphomas diagnosed?
Most aggressive lymphomas are usually diagnosed with fine-needle aspirate cytology. We can use a needle similar to the ones for vaccines, and obtained some cells from an enlarged lymph node or other mass. Some biopsies may also be performed, especially to diagnose low grade lymphomas of the intestines or lymphomas within the nose.
Other tests can be performed to stage lymphomas and assess where it has spread. These may include blood tests (complete blood count and blood smear), bone marrow aspirate, abdominal ultrasound, thoracic radiographs, liver and spleen fine-needle aspirates.
How are lymphomas treated?
In some cases, lymphomas may still be localised and can be treated with some local therapies such as surgery or radiation therapy. This is not common, with the exception of some specific anatomical forms such as nasal lymphomas. In most cases, however, the lymphoma has already spread and some sort of systemic treatment is required. This generally include standard-dose chemotherapy. A chemotherapy protocol with a combination of different drugs is usually preferred as a first-line, in particular a CHOP protocol (including prednisolone, vincristine, cyclophosphamide, and doxorubicin) or a COP protocol (including prednisolone, vincristine, and cyclophosphamide). Other drugs and chemotherapy protocols are possible. Chemotherapy drugs can be administered on their own or as part of a combination, some are administered intravenously whilst others can be given orally. They can be administered as frequently as once a week, or up to every 3 weeks. Some slowly progressive lymphomas may be treated with other drugs, including low dose oral chemotherapy at home. This is in particular the case for low-grade intestinal lymphomas, which is common in cats. Our aim is to make sure cats under treatment have a good quality of life for as long as possible.
What is the prognosis of lymphoma in the cat?
Prognoses of lymphomas vary considerably between anatomical locations and grade. We may also achieve better outcomes nowadays compared to the figures obtained from older studies. Median survival times of gastrointestinal lymphomas vary from 3 months to 2 years depending on whether the lymphoma is a high-grade or low-grade. Median survival times of high-grade lymphomas may also vary between 3 months and 1.5 years depending on the anatomical location. Our medical oncologists would be able to guide you with the information available for your cat.