Have you ever noticed a mass or lump on your dog or cat? Masses can develop anytime in a pet’s life and become somewhat more common as they age. Masses can be benign (non-cancerous) or malignant (cancerous), and it is often difficult to tell the difference just by look or feel. Dermal masses are those confined to the skin, and subcutaneous masses are ones that you can feel under the skin. You do not want to just assume something is a cyst, etc., when you notice a new mass. It is best to bring it to the attention of your veterinarian, so they can let you know if additional testing is recommended. The good news is that there are somewhat easy ways to tell if the mass is something to be worried about and removed or if it can continue to be monitored.

A fine needle aspirate is an easy, non-invasive way to get more information about what kind of mass is developing. This involves using a small gauge needle to sample the mass and obtain cells. The cells are put onto a microscope slide; the slide is stained and then reviewed under a microscope. Most of the time, this is a procedure that can be done at any vet’s office, including Express Vets. There are some areas of the body that are more sensitive (between the toes, eyelids, etc.) that may require light sedation to sample, but your veterinarian would let you know what they are comfortable with aspirating. We can often tell you if the mass is a common benign mass (like a lipoma or a sebaceous cyst) or even a malignant mass (like a mast cell tumor) from our in-house cytology alone. There are times when the sample is very cellular, and we need a pathologist to review the slide to tell us if there are signs of malignancy (cancer). In this case, we can send the slides to an outside lab to have them reviewed and will often have a report within 72 hours. Based on the results of the fine needle aspirate, we may be able to let you know if this is a mass that can be monitored or if it should be surgically removed.

There are times when a mass does not exfoliate well. This means that we are unable to obtain cells from a fine needle aspirate. If this is the case, a biopsy is recommended to get a diagnosis as to the type of mass developing and can often provide more information than a fine needle aspirate. A biopsy involves taking a piece of the tissue/mass, not just the cells. The sample is always sent to an outside lab for evaluation. Biopsies require some type of sedation because they are more invasive. This may be a form of local sedation/anesthesia or full anesthesia and surgery. Biopsies need to be done at a full-service clinic for this reason. There are different types of biopsies that can be done depending on the location of the mass and the information we are trying to obtain:

  • A punch biopsy—a small cylinder of tissue is obtained with a punch biopsy tool. This is a quick procedure that can often be done with local anesthesia or light sedation.

  • An incisional biopsy—a small piece of the mass is obtained with a surgical blade (typically a wedge-shaped piece). This procedure often requires deeper sedation or general anesthesia.
  • An excisional biopsy—the entire mass is removed under general anesthesia (or local sedation/anesthesia if a small skin tag). The mass is sent to the lab to get a diagnosis of the type, and the edges/margins will be evaluated to make sure the mass was completely removed.

When you notice a mass/bump on your pet, make sure to bring it to the attention of your veterinarian. If you are monitoring a mass and you noticed an increase in size or waxing/waning behavior (it looks larger at times and smaller at other times), it should be sampled ASAP. We can also provide a body map to help you know what has been checked, and you can notate any new masses you notice between appointments. Your vet can provide one of these services to ease your fears but can also let you know if the mass/lump should be removed before it becomes a major issue.

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