7 Types of Lumps on Dogs

Not all lumps on dogs should be a cause for alarm, but pet owners should be alert and investigate any suspicious growth or mass they find. See your vet quickly if you are concerned about a lump. The two major categories which will most concern you are benign tumors and malignant tumors. Benign tumors will not grow, or only grow very slowly; they will not change, or only change over several years. Malignant tumors are usually cancerous and very dangerous. They can grow and change quickly and spread (metastasize) throughout the body. Here is more important information about many lumps typically seen on dogs.

1. Sebaceous Cysts

Sebaceous cysts are caused by an oil producing gland in your dog's body. When this sebaceous gland is blocked, a cyst filled with white liquid forms. This cyst is benign and can be surgically removed.

2. Lipomas

Lipomas are fatty lumps often found on middle-aged dogs. They are almost never malignant.

3. Warts

Warts are a commonly seen type of lump, particularly on younger dogs. They are caused by a viral infection, and they usually do not require treatment.

4. Hematomas

Hematomas are lumps filled with blood which collect near or around the site of a trauma or injury.

5. Abscesses

Abscesses are actually sacs of pus that form around wounds and trauma sites. They fight off infection by surrounding the area with white blood cells. They are part of your dog's healthy immune system defenses.

6. Papules

Papules are common skin lesions, and they are usually associated with inflammations. They can be caused by allergies, exposure to toxic substances or irritants, or minor skin infections such as follicular infections.

7. Mast Cell Tumors

Mast Cell Tumors are among the most important to watch closely, because while they can be benign, they are more often cancerous. These tumors are formed by the cells that defend the dog's body against invasion by germs and other organisms, or foreign objects. For instance, mast cells produce the swelling around an insect bite, or the site of a vaccination.

When these cells form a tumor it is usually cancerous, and can become the deadliest form of cancer. The most important things to watch for in any tumor are signs of rapid growth and changes in color, shape and size. Go to your vet immediately when you see these.

Common Malignant Tumors

  • Abdominal tumors: These are not common, and you usually cannot see or feel a limp. Some symptoms are weight loss, bloody stool, diarrhea and great discomfort associated with abdominal pain.
  • Mammary tumors: The most common form of malignant tumor seen in unsprayed females. If you find lumps in the mammary wall see your vet immediately. Early diagnosis is critical.
  • Skin cancers: The most common form of cancer found in dogs. If you find unusual red or black spots on the skin, these could be hemangiosarcomas. Fibrosarcoma could be present when you see or feel small lumps under the skin around the spine, on the skull or in the pelvic region. Squamous cell carcinomas, or SCC, can start as sores that won't heal, or small lumps. These usually appear around the head where the fur is thin, and spread from there to the internal organs.