Olive’s family noticed a mass under her ear that appeared suddenly
Take a deep breath. Many masses on the skin are not serious, but it should prompt a visit to your vet to be sure. You should be particularly concerned if this is your pet’s first mass, if the mass is bothering the animal, the bump is growing rapidly, or if it’s on the face, mouth, limbs, or tail. Additionally, if the mass is bleeding or showing signs of infection (redness, discharge), you’ll want to have it checked right away.
What’s the first thing I need to do?
When you notice a mass on your pet, make a note of where the lesion is on the body. You may also want to take a few pictures, especially if it developed suddenly. Check the rest of the body and make a note of any other bumps or changes to the skin you observe. If the mass is small, consider carefully shaving or cutting the hair so that you can easily demonstrate the site to the veterinarian.
Next, make an appointment with your vet to have the bump checked out. It’s not important that you see the vet the same day (these appointments are typically reserved for more urgent and sick cases) but try to get a visit within two weeks if possible.
What to Expect at the Vet
Once at the veterinary office, you can show the area of concern to the veterinary staff and have it check out. Some skin bumps may be normal anatomy, such as nipples or prominent boney structures. Some bumps are due to skin infections or allergies and can be diagnosed visually. In certain cases, the bumps are ticks or other parasites (if you aren’t sure, please don’t try to pull on anything!)
Diagnostic Testing
The only way to confirm the identity of a skin mass is by evaluating some of the cells microscopically. In some cases, the mass may be too small to collect sufficient samples. In other cases, your vet may not elect to take a sample but to monitor (especially in older dogs with many masses that have previously tested benign).
In most cases, your vet will want to evaluate some cells to determine what treatment is appropriate, if any. There are a few tests they may consider:
Skin cytology: Skin cytology refers to collecting a superficial sample of cells for microscopic analysis. Your vet may collect some cells with a piece of tape, by directly applying a slide to the affected skin, or by gently scraping the skin with a blade. The cells are then visualized under the microscope, typically during the appointment. Skin cytology is best for cases in which an infectious or inflammatory disease is suspected.
Dr. Miller evaluating a patient’s skin sample
Aspirate cytology: For larger lumps in which a mass is suspected, the veterinarian may collect cells with a needle and syringe. The needle is inserted into the mass and gentle suction applied to the syringe. This collects a few cells from the inside of the lump. The veterinarian will then expel the cells onto a slide. The slide may be examined under the microscope by the veterinarian or sent to a laboratory for analysis by a specialist known as a veterinary pathologist.
In some cases, the type of tumor can be readily identified with aspirate cytology. For example, in this case, a soft circular mass was felt under the skin of a dog and a sample analyzed. The cells look like this:
Aspirate cytology of a lipoma demonstrating fat cells, also called adipocytes.
These are fat cells, called adipocytes. When only fat cells are observed, this indicates a type of benign skin tumor called a lipoma, common in middle aged and older dogs. If the lipoma is relatively small and not bothering your dog, your veterinarian may recommend simply monitoring the lump at home over time.
In another example, someone found a small flat skin mass on her cat. A small sample was taken with a needle and syringe, and this was observed:
A cluster of cells from a mast cell tumor. These tumors are relatively easy
to diagnose with a simple aspirate technique using a needle and syringe.
The cells are almost exclusively mast cells, a type of white blood cell involved in the inflammatory response. This is a mast cell tumor, the most common skin malignancy we see in veterinary patients. Mast cell tumors should be promptly removed. While many can be cured with surgery alone, further testing is needed to determine how serious the disease may be.
Inconclusive Results
In some cases, a diagnosis cannot be made with aspirate cytology alone. Some tumors don’t give off a lot of cells to interpret. In other cases, we can determine some general information about the tumor, but can’t definitively provide a specific diagnosis. In these situations, a biopsy is often recommended. Depending on the case, either a small piece or the entire lump is removed and sent to a lab for biopsy (also known as histopathology). Veterinary pathologists can then identify the type of tumor which can help direct appropriate treatment.
Olive’s aspirate identified abnormal cells. She underwent a surgical biopsy to remove the mass under her ear and confirm the diagnosis.
Should skin lumps be removed?
Whether or not surgical lumpectomy is recommended depends on a lot of factors including the patient’s age, species, preexisting health conditions, size and location of tumor, and the results of any testing.
Olive’s biopsy result was benign and she made a full recovery from her surgery!
Once your veterinarian is armed with some more information about the mass in question, they can help you navigate your options and determine if surgery, ongoing observation at home, or another treatment option is appropriate.
Dr. Sarah Miller is a small animal and exotic companion animal veterinarian at Agave Veterinary Care and Exotic Animal Hospital in Leander, TX just outside of Austin. She is dedicated to compassionate pet care, exceptional customer service and communication, advocating for independently-owned veterinary practices and their teams, ongoing continuing education, and exceptional medicine. No generative artificial intelligence (AI) was used in the writing of this work.