Sarcomas in dogs are nasty tumors. The word “sarcoma” even sounds nasty to me. Osteosarcoma (cancer in the bone) and hemangiosarcoma (cancer of the blood vessels) have very poor prognoses in dogs.
The less-known fibrosarcoma, or soft-tissue sarcoma in dogs, falls under the broad term “spindle-cell” tumor or sarcoma. A fibrosarcoma forms in the cell lines that form connective tissue, blood, fat, and muscle. Fortunately, a fibrosarcoma is typically local in nature, meaning it’s less likely to metastasize to other places in the dog’s body.
Sarcomas tend to be solid masses, although they may contain cysts. Sarcomas are often palpable in or beneath the dog’s skin. Rarely they will ulcerate to the outside. Some of the masses are slow growing while others have spurts of rapid growth.
Where Are Fibrosarcomas on Dogs?
Most fibrosarcomas are on the extremities or on your dog’s body, including head and neck. They can grow in the mouth or nasal cavity or, rarely, in bones, but most are in or just below the surface of the skin. If the cancerous growth involves nerve sheaths, your dog may be painful or have an abnormal gait.
Sarcomas tend to be associated with chronic inflammation. Causes for chronic inflammation include foreign bodies and radiation therapy. While soft-tissue sarcomas have been associated with vaccine sites in cats, that association has not been established at this time in dogs.
Middle-age and senior dogs are at greatest risk, especially large and giant breeds such as Irish Wolfhounds, Doberman Pinschers, and Golden Retrievers. Puppies rarely get fibrosarcomas, but if they do, they are VERY aggressive tumors.
Nose and oral tumors have a slightly higher incidence in male dogs. Anecdotally, this is related to more sniffing.
Typical Symptoms of Fibrosarcomas in Dogs
Fibrosarcomas often start off like any lump. Smooth, not painful, might or be movable in the skin. While tending to be slow growing, they do grow and may eventually ulcerate as they outstrip their vascular supply. This type of cancer is more likely to be locally invasive than to have distant metastases.
Fibrosarcomas can be difficult to notice right away, unless you’re a dog owner who routinely does a body check for lumps and masses (and we all should!). Depending on where the fibrosarcoma is located, you may observe oral problems with eating, drooling, or bad breath. If it’s nasal, you may notice difficulty breathing, snorting, or sneezing. If it’s on the dog’s body, you will likely feel an odd lump. Don’t forget to do regular full body scans with your hands, including between the toes, down the legs, and under the belly.
If you bring your dog into the vet for a lump, having this information with you may be help with deciding the next step:
- When did you first notice the lump?
- Has it been growing?
- Does the lump seem painful?
- Has your dog acted abnormally (pain, not eating, no energy)?
Diagnosing Sarcomas in Dogs
Diagnosis is generally by a fine-needle aspirate. Your veterinarian will look at stained slides and likely send the slides to a veterinary pathologist. An alternative is a biopsy, which can be surgical slice of the mass or an excisional biopsy, where the plan is to remove the entire growth.
You may be surprised when you pick your dog up after a biopsy or surgical removal of a sarcoma. While the growth might have felt like a grape-sized mass, the incision will often be much bigger. That is due to the propensity of these cancers to be locally invasive. Your veterinarian wants “clean margins,” which means no sign of cancerous cells when tissue samples are examined by a pathologist.
Treatment for Sarcomas in Dogs
Depending on how aggressive the dog’s sarcoma is, radiation therapy may be recommended as a follow-up treatment. Chemotherapy has not been as successful but may work for some cancers. Many of these masses will recur so periodic rechecks are important.
Be sure to ask your veterinarian when you should return for checkups, how long the recovery will be from surgery, what symptoms might indicate an emergency, and if there are any activity changes required.
The existence of these soft-tissue sarcomas serves to remind dog owners of the need to do a hands-on evaluation of their dogs, ideally once a month. If you identify any lumps, rack their growth and appearance (take pictures and measurements!). If there is any question in your mind, have your veterinarian do a fine-needle aspirate.
