Health Topics  >  Skin and Coat  > Lumps and Masses

How do I know if my dog’s skin lumps are benign or malignant?

Sometimes skin masses can be present for weeks or months before they are noticed, either when you are petting your dog, or during a bath or grooming appointment.

These masses can either be benign, in which case there is no concern for spread, or malignant, meaning there is a risk of the tumor spreading to other organs in the body, so it is important to know a few simple things to look out for that raise the level of concern for any newly discovered mass.

When should I talk to my veterinarian about a skin mass on my dog?

  1. When a new mass is first identified
  2. If a known mass is growing larger (especially if it grows quickly)
  3. If a known mass changes in color – for example becoming darker
  4. If a known mass changes in texture – for example becoming firmer
  5. If your dog starts taking notice of a previously ignored mass by licking at it or rubbing it on the carpet
  6. If the mass is painful
  7. If there is discharge from the mass
  8. If the mass is located at areas where surgical removal could be difficult (a small lump on your dog’s paw may be easy to remove, but if it gets large it’ll be much more difficult)

Generally speaking, a newly discovered skin lump or mass on its own is not an emergency. However, most masses are unlikely to resolve on their own, so if you notice any of the list above, contact your veterinarian to set up an appointment.

Pro Tip: Just like with changes in human skin growths or masses, any changes in your dog’s skin mass should be brought to the attention of your veterinarian sooner rather than later.

While your veterinarian may be able to make educated guesses based on your dog’s situation, they will need to perform certain tests to be certain. Your veterinarian will likely suggest a test called a fine needle aspirate (FNA). The veterinarian will use a needle to poke the mass to collect cells, and then transfer these cells on to a glass slide. This is most commonly done with the pet awake and only takes a few minutes. 

If the mass is very sensitive or located in a hard to reach area, your dog may require sedation prior to this procedure, so they may ask you to come back on a different day. The slide is then sent to a veterinary pathology lab where it is examined to determine what cells are present. Veterinarians or technicians with a special interest and skills in cytology (the examination of cells under a microscope) may look at the slides in their own clinic instead of sending it to a lab. 

A common, inexpensive and minimally invasive diagnostic procedure for lumps is the Fine Needle Aspirate (FNA), which involves taking a sample of cells and observing it under a microscope.

Your veterinarian may also suggest a biopsy of the mass. This is where a small piece of the mass is removed using a scalpel or a round punch biopsy tool, which collects a small sample of tissue.

Biopsies generally give more information than fine needle aspirates since a large cross section of tissue can be collected, but are not recommended in every case since heavy sedation or general anesthetic is required.