Laurie Anne Walden, DVM
Most skin lumps in dogs are benign. In cats, skin masses are more likely to be malignant. It’s impossible to know if a mass is benign or malignant just by looking at it and feeling it. For diagnosis, a sample of cells from the mass must be examined under a microscope.
Veterinarians use either fine-needle aspiration or biopsy to take samples from skin masses. Fine-needle aspiration is a quick technique that doesn’t require anesthesia. The veterinarian uses a syringe and needle (about the same size used for dog and cat vaccines) to remove a small sample from the mass. The sample is transferred to a microscope slide and either checked at the veterinary clinic or sent to a laboratory for a pathologist to evaluate.
Biopsy is the removal of a section of a mass—or an entire mass, if it’s small—for submission to a laboratory. Biopsy requires at least local anesthesia; most patients need sedation or general anesthesia. Fine-needle aspiration doesn’t always yield enough cells for a definite diagnosis, so biopsy is necessary for some masses.
So when is it okay to just watch a lump to see if it gets bigger, and when should a lump be checked by a veterinarian? Masses that fit these criteria should be evaluated by aspiration or biopsy:
The advantage of evaluating masses while they’re small is that malignant skin tumors can often be cured if they’re removed early. Larger masses are harder to remove completely. Some types of skin cancer spread through the body (metastasize) over time.
Benign masses don’t metastasize to other areas of the body or damage the tissues around the mass. Once diagnosed, they can be left alone unless they become painful or annoying to the animal (for example, if the surface becomes irritated or the mass grows large enough to interfere with movement). These are some of the most common benign skin lumps in dogs and cats:[2,3]
Malignant masses are cancerous and invade the surrounding tissues or metastasize throughout the body. Some malignant skin tumors that can’t be cured with surgery can be treated with radiation or chemotherapy. Animals with skin cancer benefit from referral to a veterinary oncologist. These are some of the malignant skin tumors that affect dogs and cats:[2,3]
1. Ettinger S. See something, do something. Why wait? Aspirate. In: Proceedings of the NAVC Conference, Volume 30: Small Animal and Exotics. NAVC; 2016:720-722.
2. Gear R. Lumps and bumps: common skin tumors. British Small Animal Veterinary Congress 2008. Veterinary Information Network. Accessed August 3, 2021. https://www.vin.com/apputil/content/defaultadv1.aspx?id=3862939&pid=11254&
3. Five types of skin cancer in dogs. NCSU College of Veterinary Medicine. Accessed August 3, 2021. https://cvm.ncsu.edu/wp-content/uploads/2018/03/5-Types-of-Tumors.pdf
Photo by Anusha Barwa on Unsplash
Laurie Anne Walden, DVM
The contents of this blog are for information only and should not substitute for advice from a veterinarian who has examined the animal. All blog content is copyrighted by Mallard Creek Animal Hospital and may not be copied, reproduced, transmitted, or distributed without permission.