Canadian_Golden_Retriever[1]You were petting your dog this morning and found a bump that you’re sure was not there last week- is it serious? The short answer is: possibly.

Dogs tend to develop lumps and bumps as they age; whether these are something to worry about or can be safely ignored can be difficult to tell based on the appearance alone.

Evaluating a Mass

When presented with a lump on a dog, I first apply what oncologists call the 1-2-3 rule: 1) has the mass been present for more than a month? 2) Has it doubled in size since you first noticed it? 3) Is it greater than 3 cm (approximately 1 inch) in diameter?

If you answered yes to any of these criteria, the lump should be checked!

Step 1: What is it?

The first step is to identify what the lump is made of; most commonly these are due to infection, inflammation or, more worrisome, cancer.

To help identify the cause, we always recommend a fine needle aspirate. This involves sticking a needle into the mass to retrieve a sample of the cells that make it up. Looking under the microscope, we can make a rough determination as to whether it is a tumor.

If cancerous, is it a benign (no big deal) lump or malignant mass, requiring surgical removal or perhaps even more advanced intervention such as chemotherapy or radiation treatments? If the cells look suspicious, we may recommend sending the sample out to a pathologist for further evaluation.

  • Benign masses are a cosmetic issue but do not require immediate action.
  • Malignant tumors should be removed immediately to reduce the likelihood of spread (metastasis), to other locations in the body, such as the lymph nodes, lungs, liver or spleen.
  • Infectious or inflammatory processes may require antibiotics or additional treatment to resolve the underlying cause.
Step 2: Staging the Cancer

If a malignant tumor is found, we may recommend “staging” your dog, which involves checking your dog for potential spread of the cancer elsewhere in his/her body before surgical removal.

If the cancer has spread, this may change our recommendations regarding treatment, as removing the mass would not cure the cancer. Other treatment options may be considered before surgery in these cases.

If the cancer has not spread- excellent news! Surgery is recommended as soon as possible to remove the mass before it does migrate.

Step 3: Identifying the Mass- Specifically

Any cancerous mass that is removed should be sent to the pathologist for identification and to check the margins of the mass removal- ie: did we remove it all at surgery?

If some of the tumor remains, a second surgery or radiation treatment may be needed to destroy any remaining cancer cells before they get the chance to multiply once more.

Once identified, the pathologist can give a much more accurate idea as to prognosis and suggestions for further treatment or follow-up.


All in all, the best advice upon finding a lump on your dog is to get it checked earlier rather than later! Even tiny bumps may be the early signs of a malignant (bad) cancer, while larger bumps may be benign and your dog can live with it happily for the duration of its life.

It is best to check early, just in case- especially if surgical removal is recommended! The prognosis for your pet is much improved to catch such lumps early, rather than waiting for any potential complications to arise.