Dog’s Lesion May Be From Trauma, Infection, Even Cancer

Q. My healthy, happy 12-year-old Labrador Retriever has a small open sore on her muzzle. It has been there about a week or two now. Do you think it’s anything to be concerned about? Any idea on what it could be?

A. Thank you for sending the photos of your dog’s sore on her mouth. In veterinary lingo, we would call this sore a “lesion” because it could have a number of different causes.

Although it’s not possible to diagnose the lesion on pictures alone, it is possible to speculate on possible causes and next steps to take. Allow me to help you get into the head of a veterinarian who might be faced with this type of diagnostic puzzle.
 
The first step in obtaining a diagnosis is creating a list of large categories that would include almost all possible causes. For your dog’s lesion, here they are:

1. Trauma, for example, running into a sharp branch
2. Infection, either bacterial or yeast
3. Parasites, such as mites or lice
4. Inflammation due to an autoimmune skin disease, irritation, or allergies
5. Neoplasia, a form of skin cancer
 
Based on your dog’s age, the lesion’s appearance, and how it changes over time or responds to treatment can provide a lot more information that can help with diagnosis.

Because you have an older dog, parasites are relatively unlikely, and cancer is more likely. If your dog is fairly active and chases balls or sticks, a traumatic wound is possible. Infection or other inflammation is possible in any age dog. Does it appear to be itchy? Is there any discharge, such as pus or blood?
 
If you’re not up for taking her to your veterinarian right away, try keeping the lesion clean for several days, gently scrubbing it with a clean washcloth soaked in warm water. If it was caused by trauma or infection, it should start healing on its own. If it is not improving, or worsening, I take her to the veterinarian. Don’t use any kind of antibiotic or other ointment, since this can interfere with healing.
 
If needed, your veterinarian can perform several simple procedures including a skin scraping or fine needle aspirate to gather most of the information needed to make a diagnosis. In general, a diagnosis is arrived by ruling out all possible causes to arrive at one or two possibilities.