Lymphoma is the most common cancer diagnosed in cats, accounting for approximately 30% of all feline tumors. It is a cancer of lymphocytes — the white blood cells that form the backbone of the immune system — and can arise in virtually any organ. Feline lymphoma spans a wide spectrum from aggressive, rapidly progressive high-grade forms to slower-growing low-grade intestinal forms that owners may manage for years.
Types of Feline Lymphoma
The most common form in modern cats is alimentary (gastrointestinal) lymphoma, which affects the small intestine and, less commonly, the stomach or large intestine. Low-grade (small cell or lymphocytic) alimentary lymphoma is the most prevalent subtype overall and behaves indolently, often mimicking inflammatory bowel disease clinically. High-grade (large cell or lymphoblastic) alimentary lymphoma progresses rapidly.
Mediastinal (thymic) lymphoma primarily affects young cats and is strongly associated with feline leukemia virus (FeLV) infection. It involves the thymus and mediastinal lymph nodes, causing fluid accumulation in the chest cavity that leads to breathing difficulty. Nasal lymphoma arises in the nasal passages, causing sneezing, nasal discharge, and facial deformity.
Signs and Symptoms of Lymphoma in Cats
Alimentary lymphoma — particularly the low-grade form — produces vague, chronic gastrointestinal signs: weight loss (often dramatic, with muscle wasting most visible around the spine and hindquarters), intermittent vomiting, diarrhea, and reduced or ravenous appetite. High-grade GI lymphoma and mediastinal lymphoma progress rapidly. Mediastinal lymphoma causes open-mouth breathing and rapid breathing as pleural effusion worsens.
Diagnosing Feline Lymphoma
A definitive diagnosis of lymphoma requires cytology or histopathology. Aspirates of enlarged lymph nodes or masses can yield a rapid presumptive diagnosis. For alimentary lymphoma, endoscopic biopsy or full-thickness surgical biopsy provides samples of the intestinal wall; distinguishing low-grade lymphoma from IBD often requires specialized immunohistochemistry (IHC) or PCR for antigen receptor rearrangements (PARR) testing. FeLV and FIV status should be tested in all cats newly diagnosed with lymphoma.
Treatment Options for Cats with Lymphoma
Treatment strategy differs fundamentally between low-grade and high-grade lymphoma. Low-grade alimentary lymphoma responds remarkably well to a simple oral chemotherapy protocol: chlorambucil combined with prednisolone. The majority of cats — over 70% — achieve clinical remission, and median survival times exceed 2 years in many studies, with some cats living 4-5 years. High-grade lymphoma requires more aggressive multi-drug chemotherapy protocols. Radiation therapy is the treatment of choice for nasal lymphoma, with remission rates exceeding 80%.
What is the most common type of lymphoma in cats?
Low-grade (small cell) alimentary lymphoma is the most common form of lymphoma in cats overall, particularly in older, indoor cats. It involves the small intestine, progresses slowly, and responds well to oral chlorambucil and prednisolone.
How can I tell if my cat has lymphoma vs. IBD?
Low-grade intestinal lymphoma and IBD can look identical clinically. Distinguishing them requires intestinal biopsy with histopathology and immunohistochemistry (IHC) or PARR testing. Both conditions respond to similar initial treatment (prednisolone), but the addition of chlorambucil is the definitive treatment for confirmed lymphoma.
Is feline lymphoma painful for cats?
Feline lymphoma is generally not described as an overtly painful cancer. However, intestinal disease causes nausea and discomfort, and advanced disease with organ failure causes significant debilitation. Cats are stoic and may not show obvious pain, but weight loss, lethargy, and poor appetite indicate they are not feeling well.
Can cats be cured of lymphoma?
True cures are uncommon in feline lymphoma, but meaningful long-term remissions are achievable — particularly with low-grade alimentary lymphoma. The goal of treatment is to maximize quality of life and duration of comfortable remission.
What are the signs that a cat with lymphoma is declining?
Signs that a cat with lymphoma may be declining include worsening weight loss despite eating, increasing lethargy, complete loss of appetite, difficulty breathing, persistent vomiting or diarrhea not controlled by medications, and loss of interest in surroundings. These signs warrant a reassessment conversation with your veterinarian.