Written by Dr. Ksenia Popov DVM CVAT CCAT

Hearing the word “cancer” is one of the hardest things a pet owner can face. If your vet has noticed swollen lymph nodes or other concerning signs, it’s natural to feel overwhelmed and unsure of what comes next. The good news is that your general practice vet can start gathering important answers right away; without needing to refer you to a specialist first.

Here’s a simple guide to the tests your vet may recommend, and what they’re looking for.

Why Lymphoma Is Often Suspected First

Lymphoma is one of the most common cancers in dogs. It most often shows up as swollen lymph nodes — lumps you might notice under the jaw, in front of the shoulders, or behind the knees. Your vet may spot these during a routine exam, or you may have noticed them yourself at home.

Tests Your General Vet Can Perform

Fine Needle Aspirate (FNA)

This is usually the first step. Your vet uses a small needle to collect cells from a swollen lymph node (or other lump). These cells are put on a slide and stained with special color. It’s quick, minimally invasive, and doesn’t require sedation in most cases. The cells are then examined under a microscope, either in-house or sent to a veterinary pathologist, to look for abnormal lymphocytes (the white blood cells involved in lymphoma).

An FNA can strongly suggest lymphoma, but it may not always give a definitive answer on its own. In some cases FNA may not get enough cells to make a diagnosis and additional testing will be recommended, it is always frustrating when that happens but there are other options available, too! There are also additional stains or tests that may need to be performed on the FNA sample for lymphoma diagnosis.

Blood Work (CBC and Chemistry Panel)

A complete blood count (CBC) and blood chemistry panel give your vet a broad picture of your dog’s overall health. We recommend annual testing in dogs over the age of three, and bi-annual testing in dogs over the age of seven. These tests can reveal anemia, abnormal white blood cell counts, and how well organs like the kidneys and liver are functioning, all important information before starting any treatments, or screening for abnormalities. Bloodwork is especially important if your dog is on any medications.

There is an early blood test called the Cancer DX Screening from IDEXX – if your vet offers this test, you can ask to have it added on to your wellness panel.

Imaging (X-rays and Ultrasound)

Chest X-rays can check whether lymph nodes inside the chest are affected and look for any fluid around the lungs. Abdominal ultrasound can evaluate internal lymph nodes, the spleen, liver, and other organs. An abdominal ultrasound may need to be done by the radiologist and may not always be offered at your primary vet, but they can help you get this scheduled. These help your vet understand how widespread the disease may be, a process called staging.

Biopsy 

Biopsy means removing all or some of the suspected tissue and sending it to the lab. Some general practices will refer out to oncology or surgery for this test depending on the location of the sample site. The lab processes the tissue and are able to determine what type of tissue the cancer is coming from, and how much the cells have changed (grading the cancer cells – how abnormal they look).

What About Other Cancers?

While lymphoma is a top concern when swollen lymph nodes are present, your vet will also keep other possibilities in mind, including mast cell tumors, osteosarcoma, hemangiosarcoma, and others. Many of the same tests above (bloodwork, imaging, and FNA or biopsy) are used as starting points for investigating other cancer types as well.

When a Specialist May Be Recommended

Depending on what the initial tests show, your vet may refer you to a veterinary oncologist or internal medicine specialist for more advanced diagnostics, such as a lymph node biopsy for a definitive diagnosis, or a PARR test (PCR for Antigen Receptor Rearrangement), which can help confirm lymphoma and identify the type (T cell or B Cell).  This information can be important in guiding treatment options.

Call Your Vet

If you’ve noticed lumps, swelling, changes in energy, appetite, or anything that just doesn’t seem right with your dog, trust your instincts and reach out to your vet. Early investigation makes a real difference.

Your vet is your partner in this. You don’t need to have all the answers before you make that call, reach out to your vet if you are concerned.