Lymphoma in Cats

Key Takeaways

Lymphoma (lymphosarcoma) is a common form of cancer that causes an uncontrolled growth in the number of lymphocytes (white blood cells). 

• Most cases of lymphoma affect middle-aged and older cats, except in cases of  FeLV-caused lymphoma which mostly affects cats under five years of age

• Symptoms of lymphoma often include enlarged lymph nodes, weight loss, vomiting, and diarrhea

• Diagnostic tests such as physical examination, blood work, and diagnostic imaging help identify masses and confirm elevated lymphocyte numbers, indicating lymphoma

• Lymphoma is life-threatening and must be treated as an emergency

• Treatment may involve chemotherapy, surgical removal of masses, and steroid treatment

• When treated, prognosis depends on the location, severity, and stage of cancer

• The objective of treatment is long-term remission, not a cure

A Closer Look: What is Lymphoma in Cats?

Lymphoma can be categorized by the affected anatomical location, by grade, and by cell type.

Common locations of lymphoma in cats include:

GI lymphoma is the most common form of lymphoma in cats. Diagnosis is complicated as symptoms are indistinguishable from those of inflammatory bowel disease.

Mediastinal lymphoma usually affects young cats (less than five years of age). The mediastinum is a sheet of tissue that contains the heart, the trachea, and the esophagus. Mediastinal lymphoma is commonly associated with FeLV infection. Cats with mediastinal lymphoma have a shorter lifespan than other cats because of secondary complications, with most cats surviving 3-12 months after diagnosis.

Nasal lymphoma is a rare, localized lymphoma affecting the nose. The prognosis is good, with most cats living 1.5-2.5 years after diagnosis.

Renal lymphoma is an aggressive form of lymphoma affecting the kidneys. The median survival rate is 3 to 6 months. Half of all cats with renal lymphoma are positive for FeLV.

Lymphoma can also be present in other parts of the body and internal organs.

The grades of lymphoma refer to the rate at which the cells divide.

High-grade lymphoma: the most malignant form of lymphoma. These lymphomas tend to have a poorer prognosis and are more prone to metastasis (spreading). Most cats with high-grade lymphomas live approximately 6-8 months after diagnosis, however some forms of aggressive lymphomas have an even shorter survival time.

Low-grade lymphoma: the least malignant form of lymphoma. In most cases, these types of lymphoma have a better prognosis.

The different cell types of lymphoma are:

Small cell lymphoma is generally less malignant than all other forms of lymphoma. The prognosis is good, with most cats living 2-4 years after diagnosis.

Large cell lymphoma is a more malignant form of cancer. The prognosis is poor, and many cats live less than 60 days after diagnosis.

Lymphoma requires prompt veterinary assessment. Early diagnosis and treatment increase the possibility of prolonged remission.

Risk Factors

Lymphoma is a common malignant cancer that affects cats over ten years of age. GI tract lymphoma is the most common form of lymphoma in cats, but any organ can be affected. Cats that contract FeLV or FIV have a higher risk of developing lymphoma. Both male and female cats are subject to the risk of lymphoma. Intact, outdoor, male cats have a slightly higher risk of developing lymphoma due to their increased risk of contracting FIV and FeLV from fighting behaviors. Siamese cats and related breeds seem to be more prone to lymphoma.

Possible Causes

Lymphoma is the uncontrolled proliferation of lymphocytes. Potential contributing factors of lymphoma: 

FeLV: Feline leukemia virus can lead to proliferation of lymphocytes. Cats infected with FeLV are 60 times more likely to develop lymphoma.

FIV : Feline Immunodeficiency Virus does not directly cause lymphoma, however it increases the risk of development due to its immunosuppressive effects. Cats infected with FIV are 5 to 6 times more likely to develop lymphoma. 

• Environmental factors: studies have found that exposure to tobacco smoke, radon, and agricultural chemicals may increase the probability of developing lymphoma. 

• Immunologic factors such as immune dysfunction • Genetic factors such as breed predisposition

Main Symptoms

Main symptoms of lymphoma: 

Enlarged lymph nodes • Weight loss • Vomiting • Diarrhea • Loss of appetite

Testing and Diagnosis

The first step in diagnosis is a physical examination, which may identify enlarged lymph nodes common with this type of cancer. If lymphoma is suspected, the following diagnostics are typically performed: 

• Blood tests including a white blood cell count • Urine analysis • Biopsy of a lymph node or mass

• Diagnostic imaging, such as X-rays or ultrasound • Needle aspirate of a lymph node or mass

To definitively diagnose lymphoma and determine the type and severity, a biopsy submission is required.

Steps to Recovery

Treatment depends on the type, severity, and stage of cancer. Therapeutic plans can include:

• Chemotherapy • Radiotherapy • Steroid treatment • Surgical removal of masses

Cats with lymphoma are often unwilling to eat or drink appropriately. Supportive care that may be provided includes:

• Fluid therapy • Anti-nausea medication • Appetite stimulants

Prognosis and remission rates for lymphoma are highly variable depending on the kind, severity, stage of cancer, and whether the cat is FeLV positive. Without treatment, the prognosis is extremely poor, with most cats dying within 4 to 8 weeks from diagnosis.

Remission is the stage in which cancer cells are not detectable in the animal's system. The goal of treatment is long-term remission or improving quality of life, not a complete cure. Across all types of lymphomas, about 50-80% of cats achieve remission, lasting for an average of 4-9 months.

Prevention

While lymphoma is not contagious, FeLV and FIV are, and they can lead to the development of lymphoma. Testing, vaccinating, and keeping cats indoors are the best strategies to prevent FeLV and FIV infection.

Frequent veterinary check-ups increase the probability of early diagnosis of lymphoma which can improve the animal's chances of survival.

Is Lymphoma Common in Cats?

Lymphoma is the most common form of malignant cancer in felines. Cats that are positive for FeLV or FIV are more prone to developing lymphoma.

Typical Treatment

• Chemotherapy • Radiotherapy • Surgery • Steroid treatment

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