Skin Growth, Lump, Swelling or Mass in Dogs

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Overview of Skin Tumors in Dogs

Skin growths are lumps of tissue that are within the skin or can be felt under the skin. Dogs can develop small bumps (papules) or larger bumps (nodules) on their skin. These lumps and bumps are fairly common occurrences, especially in the older dog.

Below is an overview of skin tumors and lumps in dogs followed by in-depth information about figuring out about benign vs. malignant tumors as well as the diagnosis and treatment of treating skin tumors. 

Very often the word “lump” brings the word “cancer” to mind. However, there are many other causes of lumps. A skin growth or mass may be a malignant or benign tumor, an abscess, a cyst, a hematoma (blood-filled mass) or a reaction by the skin to an allergen (hives). Lumps are often benign accumulations of fat called lipomas. However, all lumps should be evaluated for the possibility of malignancy.

What to Watch For

Any new lump or bump should be evaluated right away, especially a lump that is rapidly growing, is warm or painful, is ulcerated or bleeding, is irregular in shape or is well attached to the tissues under the skin. Any of the above signs should prompt you to seek veterinary attention.

Diagnosis of Skin Tumors in Dogs

Your veterinarian may take a complete history. Expect to answer the following questions:

  • How long the growth has been there?
  • Has it gotten larger or smaller or changes in appearance?
  • Does the lump appear to be attached to the underlying skin?
  • How fast is it is growing?
  • Have there been any recent injuries or injections?
  • Is there only one lump or are there others?
  • Are there any changes in your pet’s behavior, such as eating less, weight loss, vomiting, diarrhea or lethargy?

    A complete physical exam will be done. Your veterinarian will pay particular attention to the appearance of the mass, whether it is hot or painful, whether it is within the skin or under the skin, if it is attached to underlying tissues and where it is located on the body. Additional tests may include:

  • An aspirate of the mass with a small needle may be done to collect cells for staining and examination under a microscope (cytology). This test usually requires no anesthesia and often leads to a diagnosis.
  • If the mass is ulcerated or draining fluid, a microscope slide may be touched to the fluid to make an impression for microscopic examination.
  • A biopsy may be taken to send to a veterinary pathologist for examination. The biopsy may involve removing the entire mass or removing a piece of the mass.
  • A piece of tissue may be submitted for culture if infectious agents such as bacteria or fungi are suspected.
  • Treatment of Skin Tumors in DOgs

    Treatment depends on the cause of the mass. There is no specific treatment for all skin growths.

    Home Care

    Give all medications as instructed and observe masses closely for growth, heat, redness and pain.

    If the growth has been removed or biopsied, keep your dog confined to allow for healing. Observe the incision site closely for drainage, swelling, redness, heat or pain.

    In-depth Information on Skin Tumors in Dogs

    A skin mass or lump can be within the skin, in the tissues under the skin or attached to the skin and underlying tissues. Thus, any proliferation of cells, pocket of fluid or debris, or swelling of the dog’s tissues can cause a mass. The health impact depends on the severity of the cause of the growth and the success in treatment of the problem.

    The most common causes of skin growth are tumors, malignant and benign, bruises, infections and other causes.

    Malignant Dog Tumors

    Malignant tumors are proliferations of abnormal cancerous cells that endanger the dog by either invading nearby tissues or spreading to other areas of the body (metastasis). There are too many types of skin tumors to list here, but some of the more common ones are:

  • Mast cell tumors. These are made up of great numbers of mast cells, a type of cell that is normally found within the skin. These cells normally release substances that are involved in allergic and immune responses. The massive amounts of these substances that can be released from tumors can be very dangerous to the animal. Tumors of this type can invade locally and metastasize.
  • Melanomas. These are tumors of the cell type that provides pigment to skin. They may be malignant or benign. Melanomas on the feet or in the mouth are likely to be very aggressive and dangerous. These tumors are usually black in color.
  • Fibrosarcomas. These tumors affect the cell type that helps to make up the connective tissue found under the skin. They rarely metastasize but are very destructive locally.
  • Squamous cell carcinomas are malignant tumors of skin cells that often occur at areas of unpigmented or lighter colored skin due to damage from the sun. They rarely metastasize but are destructive locally. They may also be non-solar induced.
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