Lymphoma is a common cancer in pets, and a systemic condition that can involve multiple body systems, including the eye. Our Veterinary Vision Center team wants to provide information about ocular lymphoma, so you know what to expect in case your pet is affected.

Pet lymphoma basics

The term “lymphoma” describes a diverse group of cancers that originate from white blood cells (WBCs) called lymphocytes, which help the immune system fight infection. They are highly concentrated in organs such as the lymph nodes, spleen, and bone marrow that play a role in the immune system, and these are the organs most commonly affected, although lymphoma can affect any body system. Lymphoma is the most common cancer in cats and accounts for about 20% of cancer in dogs. The four most common lymphoma types are:

  • Multicentric lymphoma — Multicentric lymphoma is the most common form in dogs, accounting for approximately 80% to 85% of cases. The condition is closely associated with feline leukemia in cats, and prognosis is not good if the cat is feline leukemia positive. The condition affects lymph nodes throughout the pet’s body, with rapid lymph node enlargement (i.e.,  3 to 10 times normal size) the most obvious clinical sign. The swellings feel like firm lumps that move freely under the skin and are not painful. Affected pets may develop fever, lethargy, decreased appetite, and weakness as the disease progresses. 
  • Alimentary lymphoma — Alimentary lymphoma is the most common form in cats, and the second most common form in dogs, and affects the gastrointestinal tract and the surrounding lymph nodes. Affected pets exhibit signs including vomiting, abdominal pain, decreased appetite, diarrhea, and weight loss.
  • Mediastinal lymphoma — Mediastinal lymphoma attacks chest lymphoid organs, such as the thymus and mediastinal lymph nodes. Affected pets exhibit signs including difficulty breathing, fluid accumulation in the chest, increased thirst and urination, and swelling in the face and front limbs.
  • Extranodal lymphoma — Extranodal lymphoma occurs when the disease targets a particular organ, such as the eyes, skin, kidneys, lungs, or central nervous system. Signs depend on the body system affected. 

Pet lymphoma diagnosis

If lymphoma is suspected, your veterinarian will take a sample of the affected organ, which is most commonly performed by fine needle aspiration, in which a needle is inserted into the lymph node and organ, and a sample extracted for cytologic or histopathologic evaluation. Other diagnostics, such as blood tests, urinalysis, X-rays, ultrasound, and bone marrow aspiration, may be recommended to stage the lymphoma. Stages include:

  • Stage I — Stage one lymphoma is rarely diagnosed in pets, and involves only a single lymph node.
  • Stage II — Stage two lymphoma is also rare in pets, and involves lymph nodes only on one side of the pet’s diaphragm (i.e., the sheet of muscle separating the chest and abdominal cavities), meaning that only the front of the pet’s body or the rear is affected.
  • Stage III — Stage three lymphoma describes generalized lymph node involvement throughout the pet’s body.
  • Stage IV — Stage four lymphoma is diagnosed when the liver or spleen is involved.
  • Stage V — Stage five lymphoma is diagnosed when the bone marrow, nervous system, or other location is involved.

Pet ocular lymphoma

The eye’s uveal tract is one of the most vascular areas in the body, making the organ a target for systemic diseases such as lymphoma. Malignant lymphoma is the most common secondary tumor in the dog’s eye, and can also affect cats. Potential ocular manifestations include uveitis (i.e., inflammation inside the eye), uveal thickening, corneal surface lesions, and conjunctival and third eyelid involvement, with both eyes typically affected. Ocular abnormalities found in a lymphoma patient are typically classified as stage V lymphoma, although, rarely, malignancy is not found in the peripheral lymph nodes, and the condition then is classified as presumed solitary ocular lymphoma (PSOL).

Pet lymphoma treatment

Lymphoma treatment typically involves systemic chemotherapy. Most lymphomas are chemosensitive, and systemic chemotherapy is effective in about 60% to 90% of pets. Combination chemotherapy protocols, compared with single agent chemotherapy, tend to be more effective, and the treatment should be tailored to the presentation stage and the organs involved. When ocular involvement is present, topical anti-inflammatories can decrease signs and help prevent complications, such as glaucoma and vision loss. In cases classified as a PSOL, the eye should be enucleated to prevent metastasis. 

Pet lymphoma prognosis

Your pet’s prognosis will depend on their cancer stage when treatment begins and the treatment protocol employed. Generally, pets who don’t receive treatment have an expected survival time of four to six weeks. Pets can go into remission after chemotherapy, and most pets remain in remission for about eight to nine months. The average survival time with chemotherapy is about one to two years. 

Ocular manifestations are sometimes the first sign that your pet has lymphoma, and the sooner the disease is detected, the better your pet’s prognosis. If your pet is affected by ocular lymphoma, contact our Veterinary Vision Center team, so we can devise a treatment strategy to preserve their vision and decrease their discomfort.