Masses: Assorted lumps and tumors of dogs and cats

Masses Neoplasias Lumps Lipomas and Tumors in Dogs and Cats

There’s a “mass” about your dog or cat. Otherwise I doubt you’d be looking at this page.

Here’s two fun facts about masses in dogs and cats:

  1. A random “mass” in a dog is likely to be benign, the odds are 25% malignant to 75% benign. Sight unseen.
  2. A random “mass” in a cat is likely to be malignant. The statitistic is quite  the opposite of dogs with 25% being benign and 75% being malignant.

Variables include the breed, and the location of the mass. For example: A mass in the spleen of a Boxer is COMMON and is often malignant. [Hemangiosarcoma] although, not always.A black or heavily pigmented mass in the MOUTH of a dog is often a melanoma. ALthough, not always.

An erosive lesion “eating” away a cats ear, lip or face is often Squamous Cell Carcinoma, although, not always.

And frankly, none of it matters if:

  1. A dog or cat is impossibly elderly or weak
  2. If chemotherapy or radiation is out of the question (And it should be)
  3. If surgical intervention is impossible, ill-advised or is out of the question.
  4. The cancer is known to be a fast-moving malignancy already disfiguring the pet.

Still, franchise veterinary medicine wants to know WHAT the mass is, WHERE it may have spread to, HOW it’s impacting other organs, the dog or cat’s fitness for advanced intervention, and more. Why? Certainly not to increase the chances of success in treatment: To this day (012224) oncology hasn’t wrought much in the way of actual cures for various common malignancies in dogs and cats. But it can buy time.

So if you’re reading this, we have found a “mass” in your dog. And you should know a few things.

We can stick a needle in a mass to help determine cells that are present. But if I miss the mass and hit a strand of normal cells INSIDE the mass, or the sample has too much juice or blood in it –  the expense is for naught. They’ll report normal cells or not enough cells and they’ll request a PIECE of the mass. Anticipating this, I like to skip the needle biopsy andsometimes recommend just “kicking off the case” with a biopsy. Like, a piece.

But then wait. If I’m going to per-op the pet, apply general anesthesia, prep the area and remove a wedge of the mass, WHY DON’T I REMOVE THE MASS? After all, they’re just going to make me go in and remove it later anyway. Also, if it’s inoperable why are we doing any kind of biopsy at all anyway?

SO I usually like “Excisional Biopsy” means removing the thing, and then sending it to the lab and figuring out what it is.

But then wait. If the dog is 17 years old and the mass was only removed for location, behavior, color or impact on other mechanical systems, do we really NEED to know what it was? Are we planning chemo or radiation? Re-surgery for wider margins? If not, then isn’t EXCISION all that was needed?

So, unless I am wondering about the identity of a mass in a dog “young enough for it to matter” I’ll resort back to me ALMOST ALWAYS COMMENT:

“If it grows it goes.”


Author: Dr. Erik Johnson
Dr. Erik Johnson is the author of several texts on companion animal and fish health. Johnson Veterinary Services has been operating in Marietta, GA since 1996. Dr Johnson graduated from the University of Georgia College of Veterinary Medicine in 1991. Dr Johnson has lived in Marietta Georgia since 1976.