Symptoms of feline lymphoma include lethargy and unexplained weight loss and loss of appetite. The owner may also be able to feel lumps in the cat's lymph nodes, especially in the chest or the digestive system. Other symptoms are vomiting, mouth breathing, constipation and diarrhea. There may also be blood in the cat's stool. This can present as black, tarry stools or stool with fresh blood in it. The cat may urinate more than usual and be unusually thirsty.
These symptoms depend on the type of lymphoma the cat suffers from. The mediastinal form is a type of lymphoma that attacks the lungs and the spaces between the lungs and their protective membranes. The alimentary form of lymphoma attacks the cat's gastrointestinal tract, while the multicentric form involves the cat's lymph nodes. The renal form of feline lymphoma attacks the kidneys.
Feline lymphoma is thought to be caused by the feline leukemia virus and the feline immunodeficiency virus. Cats who are most at risk for feline lymphoma are outdoor cats who haven't been vaccinated against either of these viruses.
Most types of feline blood cancers are lymphomas, or cancers that affect the cat's white blood cells. As of 2015, feline lymphoma is not curable, though the life of the animal can be prolonged through chemotherapy.