8 Types of Dog Tumors and How to Treat Them Part 1

That’s because cancer is both extremely common in dogs and a leading cause of death. The National Cancer Institute’s Center for Cancer Research says that about 6 million of the 65 million pet dogs in the United States will be diagnosed with cancer each year.

Additionally, in 2011, researchers at the University of Georgia College of Veterinary Medicine found that cancer was the most common cause of death in older dogs. (It’s also the leading cause of death for 71 of the 82 breeds studied.)

Erika Krick, DVM, an assistant professor of oncology at the University of Pennsylvania School of Veterinary Medicine says signs of cancerous tumors often include skin wounds that don’t heal or unexplained weight loss. That said, many dogs often have lumps and bumps that are completely benign. “If you notice something new, take your dog to the vet,” she says. “You need to know what it is, and the smaller it is when it’s diagnosed, the easier it is to treat.”

Not all tumors in dogs are cancerous, but all of them should be evaluated by your veterinarian. Continue reading for eight common and notable types of tumors in dogs, the breeds that are most susceptible, and what treatment looks like for each.

Mast Cell Tumors

Krick notes that mast cell tumors are one of the most common type of canine skin tumors. “These grow quickly and are usually red and very itchy,” she says.

That’s because the lumps contain a chemical called histamine, one of the substances responsible for itching associated with allergies. “Histamine tells the stomach to make more acid, so dogs with these tumors are also at risk for gastrointestinal ulcers,” Krick says.

Short-faced dogs—including Boxers, Pugs, and French Bulldogs—are most at risk for mast cell tumors. Typically, these breeds develop lower-grade, less aggressive tumors, while Chinese Shar-Peis are prone to very aggressive mast cell tumors. Unlike many tumors that are significantly more common in older dogs, there is a weaker correlation between age and mast cell tumor susceptibility.

Krick says treatment begins with a fine needle aspirate to retrieve a cell sample and diagnose what type of tumor you’re dealing with. Surgical removal follows. The tumor(s) should always be sent to a pathologist for grading (a measure of how aggressive the cancer is) to help determine the need for further treatment.

Lipomas

Christine Swanson, DVM, a veterinary medical oncologist and assistant professor at the College of Veterinary Medicine at Michigan State University, calls this benign fatty tumor very common and notes that many different breeds are prone to developing them. Lipomas usually feel like a relatively soft mass that can be moved around underneath a dog’s skin.

They vary in size, and most of the time, they’re not a serious issue. A fine needle aspirate is done to confirm the benign nature of the tumor, and the tumor is usually only removed if it’s bothersome to the dog’s normal movement or activity, Swanson says.

Osteosarcoma

Large and giant breeds like Greyhounds and Great Danes are most susceptible to this bone cancer that often affects a dog’s legs

“Most dogs that eventually get diagnosed with this come in because they're limping,” Krick says. “It's not as common that a bone in the spine would be affected.”

An x-ray is conducted on the area in question to rule out things like arthritis. Sometimes a biopsy is necessary to differentiate osteosarcoma from other conditions that can look similar on x-rays. If cancer is diagnosed, amputation followed by chemotherapy is the treatment of choice, Krick says, though some dogs are candidates for a limb-sparing procedure. In these cases, only the affected area of the bone is removed, and either a bone graft or a metal rod replaces it.

“This is an option for tumors in the distal radius, or the lower bone in the front leg,” Krick says, although limb-sparing surgery can also be considered for osteosarcoma at other sites.