What Is Lymphoma? 

Lymphoma is a cancer of the lymphocytes. Lymphocytes are cells involved in the immune system and travel throughout the body in the blood and lymphatic vessels; therefore, lymphoma is always considered to be a systemic, not localized, disease.

• Lymphoma is connected with feline leukemia, a viral infection. More cats are now being vaccinated for feline leukemia; therefore, lymphoma is becoming less common. It is still frequently seen, accounting for approximately 30% of new feline cancer diagnoses.  (VCA)

Lymphatic System

The immune system protects the body from foreign substances, infection, and diseases. The lymph system is made up of the following:

• Lymph: Colorless, watery fluid that carries white blood cells called lymphocytes through the lymph system. Lymphocytes protect the body against infection and the growth of tumors. There are three types of lymphocytes:
  • B lymphocytes that make antibodies to help fight infection. Also called B cells. Most types of non- Hodgkin lymphoma begin in B lymphocytes.
  • T lymphocytes that help B lymphocytes make the antibodies that help fight infection. Also called T cells.
  • Natural killer cells that attack cancer cells and viruses. Also called NK cells.
• Lymph vessels: A network of thin tubes that collect lymph from different parts of the body and return it to the bloodstream.
• Lymph nodes: Small, bean-shaped structures that filter lymph and store white blood cells that help fight infection and disease. Lymph nodes are located along the network of lymph vessels found throughout the body. Clusters of lymph nodes are found in the neck, underarm, abdomen, pelvis, and groin.
• Spleen: An organ that makes lymphocytes, filters the blood, stores blood cells, and destroys old blood cells. Thymus: An organ in which lymphocytes grow and multiply
• Tonsils: Two small masses of lymph tissue at the back of the throat. The tonsils make lymphocytes.
• Bone marrow: The soft, spongy tissue in the center of large bones. Bone marrow makes white blood cells, red blood cells, and platelets.
• Lymph tissue is also found in other parts of the body such as the stomach, thyroid gland, brain, and skin. Cancer can spread to the liver and lungs.

Types of Lymphoma in Cats

Lymphoma can occur in several areas of a cat’s body. Before widespread vaccination for feline leukemia virus, lymphoma tended to occur outside the GI tract.

Intestinal lymphoma is most common, making up more than 50% of all lymphoma cases.

Typically, cats with lymphoma are older, usually 10 to 12 years old. Cats with intestinal lymphoma can have either a low-grade version, in which they experience thickening of their intestines, or a high-grade version in which large masses are formed in the intestines.

Mediastinal Lymphoma: Occurs when cats develop masses in their chest, either in the lymph nodes or the thymus gland. The mediastinum is the connective tissue holding the heart and lungs and soft tissue in the chest in place. Mediastinal lymphoma is more common in younger cats. Most of these cats are positive for feline leukemia virus. Siamese cats are more prone to developing this type of lymphoma.

Renal Lymphoma: Occurs when lymphoma cancer develops in the kidneys. This type of lymphoma looks a lot like kidney disease, with symptoms including decreased appetite, vomiting, weight loss and an increase in drinking and urinating. Unfortunately, renal lymphoma often spreads to the nervous system, particularly the spinal cord and brain, and can be quite aggressive.

Nasal Lymphoma: Occurs when cats develop a tumor in the nasal cavity.  This leads to frequent sneezing and nasal drainage. Sometimes, swelling can be seen on the bridge of the nose in advanced disease.

Multicentric Lymphoma: This cancer is primarily in the lymph nodes of the body. Cats that develop multicentric lymphoma are often affected by either the feline leukemia or feline immunodeficiency virus. While this form is uncommon in cats, it is the most common form of lymphoma in dogs.

Common Sites of Lymphoma in Cats

Sites of lymphoma in cats:

Alimentary or Intestinal Lymphoma– By far the most common lymphoma in cats, this type of lymphoma affects the guts.

• Intestinal lymphoma can actually be split into two further types- small cell lymphoma, and large cell lymphoma.
  • Small cell lymphoma is a slow-growing, cancer-causing gut thickening, whilst large cell lymphoma creates hard tumors in your cat’s guts and/or stomach.
  • Large cell lymphoma in cats is far more aggressive and has a poorer prognosis.

Mediastinal Lymphoma– This type of lymphoma grows in your cat’s chest, usually between their lungs.

• Over time, it can grow large and put pressure on the lungs and heart.
• It’s more common in younger cats and those with FeLV.

Renal Lymphoma– Lymphoma can also affect the kidneys, causing symptoms similar to chronic kidney disease as the kidney cells are replaced by cancer cells.

Nasal Lymphoma– Nasal lymphoma affects the nose of cats and usually starts as a facial swelling. In about a quarter of cases of nasal lymphoma, the cancer has spread to other parts of the body.

Miscellaneous Lymphoma Types in Cats

There are also less common forms of lymphoma affecting the nerves, the lymph nodes, or other sites in the body.

• Multi-nodal lymphoma/multicentric lymphoma, cutaneous lymphoma, mesenteric lymphoma, ocular lymphoma, and spinal lymphoma are all other types of lymphoma in cats.
• There is some evidence that cutaneous lymphoma in cats is becoming more common.