Lymphoma in cats is a cancer of the lymphatic system, which is the combination of lymphocytes (blood cells) and organs (lymph nodes, etc.). It can affect many systems in a cat's body, and is the most common cause of spinal cord tumours.

According to The Royal Veterinary College, feline lymphoma is the most commonly diagnosed cancer in cats. There are many types of lymphoma in cats, but the most common is intestinal lymphoma, also known as gastrointestinal (GI) or alimentary lymphoma. A variety of factors will determine how this cancer might affect your cat.

Causes of lymphoma in cats

The onset of feline lymphoma has been linked to the feline leukaemia virus (FeLV), and, to a lesser extent, feline immunodeficiency virus (FIV). Cats who are positive for feline leukaemia generally develop cancer at a younger age. These days, because there's widespread testing for and vaccination against FeLV, lymphoma is less common in younger cats. Cats who are negative for the virus tend to develop lymphoma at an older age. 

The Blue Cross says that exposure to tobacco smoke may increase the risk of lymphoma in cats. They explain that, while secondhand smoke may be harmful to all pets, cats are especially vulnerable. Not only do they breathe in smoke from the air, but while self-grooming, they may also ingest toxic particles from smoke that has infiltrated their fur.

Types of lymphoma in cats

Because the lymphatic system interacts with every system in the body, lymphoma can affect any of these organs. The main types of lymphoma include:

• Alimentary (digestive tract)
• Mediastinal (chest)
• Renal (kidneys)
• Nasal (nose)
• Spinal (spine)
• Cutaneous (skin)
• Multicentric (meaning multiple organs are affected, most often the spleen and liver)

Signs of lymphoma in cats

Signs of lymphoma in cats depend on which organs are affected. Here are some of the signs to look out for according to where the lymphoma is located:

• Digestive tract: Vomiting, diarrhoea, constipation, loss of appetite, weight loss, lethargy and bloody stool.
• Chest: Open-mouth breathing, coughing, loss of appetite, weight loss and regurgitation.
• Kidneys: Increased drinking and urinating, weight loss and loss of appetite.
• Nose: Chronic nasal discharge, bloody nose, swollen nose, sneezing, loss of appetite, eye discharge and noisy breathing.
• Spine: Weakness or paralysis of the back legs.
• Skin: Itching, hair loss and bleeding skin tumours.

If you notice any of these signs in your cat, immediately contact your veterinarian. They can diagnose your cat's condition and determine the best treatment.

Diagnosis of cat lymphoma

Lymphoma is diagnosed using a combination of information. If your vet suspects your cat has lymphoma, they'll ask you about your cat's history and lifestyle. They'll likely follow up with a physical examination of your cat, laboratory testing (including blood tests, urinalysis, and testing for FeLV and FIV) and imaging studies, such as radiographs and ultrasounds.

The testing that your vet recommends will vary depending on the type of lymphoma they suspect. If there's a mass or swollen lymph node, for example, they may also take a biopsy. This involves taking a small sample of the affected tissue and examining it for cancerous cells.