When people hear the word “lump,” they often think of cancer. In reality, most lumps you’ll find while petting or grooming your dogs aren’t serious—but it’s a good idea to ask your veterinarian to check them out anyway.
Skin lumps, both benign and malignant, are common in dogs. Benign tumors usually grow slowly and stay put. Malignant tumors, or cancer, often grow rapidly, and they may spread to other organs or bones. And not all lumps are tumors. What’s the difference? A tumor is a new growth of tissue, while many other lumps are caused by an accumulation of cells or fluid under the skin.
Causes
If you find a lump on your dog, don’t panic. Consider these common causes of lumps—most of which aren’t life-threatening:
Apocrine cysts are firm masses beneath the skin caused by obstructed skin glands. These benign cysts sometimes rupture like a pimple, which often clears them up.
Abscesses are painful lumps that may form because of localized infection from a bite wound or foreign object. These pockets usually contain a large amount of pus and blood and can rupture.
Hematomas occur when blood accumulates under the skin after trauma. This blood-filled swelling appears as a lump or bruise and is usually painful. A swollen ear flap indicates an abscess or hematoma. If your pet violently shakes his head because of an itchy ear problem, he may develop an ear hematoma.
Injection-site reactions occur when dogs develop a knot under the skin after the doctor administers an injection. These tender lumps usually fade in a few days to weeks. In rare cases, a cat may develop an adverse reaction to certain ingredients in injectable medications or vaccines, causing a malignant tumor known as a fibrosarcoma to develop at the injection site.
Lipomas, which are common in overweight pets, are benign tumors consisting of soft smooth clumps of fat cells that can grow very large. They’re found most often on the chest, abdomen, and front legs.
Histiocytomas are benign growths that often affect young dogs. They’re usually small, firm, and dome- or button-shaped and appear on the head, ear flaps, or legs. They often disappear with no treatment.
Sebaceous gland hyperplasia occurs when the glands that secrete sebum (the oily material that lubricates the skin) grow rapidly. These benign tumors are raised and can be smooth or wart-like in appearance and often are found on the legs, torso, or eyelids.
Malignant skin tumors signs include noticeable enlargement of the lump or a sore that won’t heal. Early detection is important, so always ask your veterinarian to check out any bump on your dog. Mast cell tumors are the most common malignant skin tumors in dogs.
Regular grooming will help you identify changes in your dog’s skin and coat. A weekly brushing, daily petting, and lots of love and attention are your pet’s first defense.
What your veterinarian will do
Your veterinarian will easily recognize some skin lumps, like lipomas and cysts. To identify other lumps, your dog’s doctor will use a fine needle to obtain a tissue sample and then examine the cells under a microscope. If your veterinarian suspects cancer, he or she will recommend a biopsy, which involves removing part or all of the tumor and sending it to a pathologist for identification. Biopsy usually requires sedation or anesthesia.
Treatment for large hematomas, ear hematomas, or an abscess involves draining the pocket and administering oral antibiotics as needed.
If your dog’s growth is benign, your veterinarian will decide whether to remove it based on the tumor’s location and size. Malignant tumors, however, often require surgery, chemotherapy, or radiation therapy.
In most cases, lumps on your dog’s skin are more of an eyesore than an emergency—but leave that diagnosis up to your veterinarian.
