Also known as lymphosarcoma, lymphoma is a malignant cancer of the lymphocytes, cells that can be found in almost every organ in the body. Part of the Lymphoid system, lymphocytes play an important part in the immune system. Unsurprisingly, lymphoma is also the most common form of cancer found in cats, accounting for 33 percent of all feline tumors.
Types of Feline Lymphoma
Since lymphocytes are found almost everywhere in the body, several major body systems are subject to feline lymphoma. This includes the:
- Multicentric: This type of lymphoma, the most common in cats, can be found anywhere lymph nodes are located, including under the jaw, in the groin area, or under the top of the front leg. Because these lymph nodes are close to the surface, bumps may be readily visible. Some cats may have multiple tumors, hence the multicentric designation. It is less common than the other forms of lymphoma.
- Mediastinal: Tumors of the thymus gland can grow very large, which causes breathing difficulty and coughing. If it grows large enough to press on the esophagus, it can cause difficulty swallowing. Tumors of the thymus gland are most common in young cats—usually two years old or younger—and commonly affect Siamese and Oriental cats.
- Alimentary: Tumors occur in the gastrointestinal tract, abdomen, liver and typically target older cats, ranging from 9 to 13 years and older.
- Renal: Lymphoma of this type occurs in the kidneys and is the worst form of lymphoma that occurs in cats. The median survival rate is between three and six months.
- Solitary: This catch-all phrase includes those body systems not included in the above types of lymphoma. They may include the nasal cavity (most common), the skin, or the central nervous system.
Symptoms of Feline Lymphoma
The symptoms of feline lymphoma differ between the types. Cats with mediastinal lymphoma typically display open-mouth breathing, coughing, a loss of appetite, and weight loss. Animals with alimentary lymphoma often don't eat, seem lethargic, and vomit or have constipation or diarrhea. While cleaning the litter box, you might see black or tarry stools or stools with blood in them.
Cats with multicentric lymphoma typically experience swollen lymph nodes, a loss of appetite, weight loss, weight loss, or depression, while those with renal feline lymphoma will also display loss of appetite but also vomiting, weakness, and increased urination and thirst (known as polyuria and polydipsia, respectively). The solitary form of lymphoma will manifest in a variety of ways, depending on where it's located.
Diagnosing Feline Lymphoma
Any unusual symptoms or combinations of symptoms should serve as red flag warnings that an urgent veterinary appointment is called for. That is why it is vital that you know your cat's normal physical condition so that you can spot important variances immediately, and know it's time to call the vet.
Your veterinarian will give your cat a thorough physical, and based on the findings, plus your description of the cat's symptoms, will order one or more of the following diagnostic tests:
- Complete Blood Count (CBC)
- Serum Biochemistry Panel
- Endoscopy of the Gastrointestinal Tract
Treating Feline Lymphoma
The treatments given to humans for cancer, such as chemotherapy, are also given to cats with lymphoma. However, in the case of chemotherapy, it is given to cats, not to achieve a cure, but to extend the cat's life as long as possible, while maintaining as high a quality of life as possible. It is a matter of balance, and often the dosages or the combinations of chemotherapy may change as needed, to attain that end goal while minimizing side effects. Alternative treatments, depending on the type and location of the tumors, are surgery or radiation.