Home » Pet Health » Cancer 101 » Detecting Cancer in the Lymphatic System


Detecting lymphoma can be challenging for pet owners because lymphoma is not usually painful for your pet. You may notice swollen lymph nodes just under your pet’s skin when giving them a rub. Although this may indicate lymphoma, enlarged glands can also be a common symptom of stomach flu and influenza. It can therefore be challenging to detect lymphoma in the early stages. Such changes will only be noticeable when a tumor in the lymph nodes has grown large. Pet owners rarely identify lymphomas on their own. Therefore, regular vet appointments and physical checks will help to ensure swollen lymph nodes are detected.

In less common forms of lymphoma, such as gastrointestinal lymphoma (”alimentary”), secondary symptoms depend on which specific organ is affected by cancer. Alimentary lymphoma, for example, can cause gastrointestinal issues, such as diarrhea or weight loss, while mediastinal lymphoma, often found in the chest, can result in shortness of breath.

If your vet suspects that your pet has lymphatic cancer, they may perform a short procedure known as a lymph node biopsy, which involves the removal of a small sample of lymph tissue for examination. A needle biopsy (removing a small amount of tissue with a needle) and a lymph node dissection (surgical removal of a small piece of the lymph node) are techniques used to obtain the tissue sample. In most circumstances, your vet will choose the needle biopsy first, as it is less invasive. They then observe the tissue samples under a microscope. If they can’t obtain enough information, they may turn to the dissection to gain a better tissue sample to determine the cancer type and stage.

There are five diagnostic stages for your pet’s lymphoma. The stages are differentiated by the body parts affected and to what extent, as seen below:

    • Stage I: Only one lymph node is involved.
    • Stage II: Lymph nodes are enlarged on only one side of your pet’s body, either the front half or the back half.
    • Stage III: Enlarged lymph nodes are on both the body’s front and back halves.
    • Stage IV: The liver or spleen is affected by cancer.
    • Stage V: Additional organs are affected by cancer.

Finding a lump on your pet can be unsettling. But if you take your furry friend for regular vet checks, note any unusual growths when you pet them, and monitor their behavior for signs of illness, you may catch things early. And remember, swollen lymph nodes may appear for different reasons. When your pet exhibits swollen glands, discuss with your vet the potential causes and be assured that treatments are available.

The Pet Cancer Foundation’s Website Editorial team is comprised of veterinarians, veterinary oncologists, and veterinary technicians, as well as scientific writers and editors who have attained their PhD’s in the life sciences, along with general editors and research assistants. All content found in this section goes through an extensive process with multiple review stages, to ensure this extended resource provides pet families with the most up-to-date information publicly available.

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Last Updated: October 21, 2022

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The following sources were referenced to write the content on this page: 

Cowell, RL, Dorsey, KE, Meinkoth, JH 2003, ‘Lymph node cytology’, Vet Clin North Am Small Anim Pract, vol. 33, no. 1, pp. 47-67.

Liptak, JM & Boston, SE 2019, ‘Nonselective lymph node dissection and sentinel lymph node mapping and biopsy’, Vet Clin North Am Small Anim Pract, vol. 49, no. 5, pp. 793-807.

Zandvliet, M 2016, ‘Canine lymphoma: a review’, Vet Q, vol. 36, no. 2, pp. 76-104.

The Pet Cancer Foundation’s medical resource for pet owners is protected by copyright.

For reprint requests, please see our Content Usage Policy.