A Guide to Soft Tissue Sarcoma in Dogs

The veterinarian's upbeat manner and long list of potential treatment options were all somehow forgotten after her answer to my question about a prognosis. In general, she admitted, about a third of dogs die of causes related to their soft tissue sarcomas. The rescued seven-year-old Newfoundland on the exam table would have to see a veterinary oncologist.

What is Soft Tissue Sarcoma in Dogs?

Soft tissue sarcomas in dogs are pretty common. They account for around 15 percent of all skin and subcutaneous cancers in dogs, according to the Animal Cancer & Imaging Center. However, not all of them are malignant.

This type of cancer arises in mesenchymal tissues. Examples include cartilage, blood vessels, fibrous connective tissue, nerves, fat and muscles.

For most of these tumors, vets uncover no cause. Because of the way they grow, they're difficult to completely remove with surgery and tend to recur.

A soft tissue sarcoma can occur in any part of the dog's body. One common type is a tumor that originates in adipose, or fat, tissue. It's called a lipoma if benign or a liposarcoma if it turns out to be malignant. Another common tumor is a fibroma, a benign growth that begins in a dog's fibrous tissue. If cancerous, it's known as a fibrosarcoma, the Pet Cancer Center reports.

Most soft tissue sarcomas occur when a dog is middle-aged or older. Pets that are large breeds are prone to this disorder. Quite often, an owner discovers the tumor as a lump while petting or grooming the dog.

Diagnosis

While doctors have at their disposal state-of-the-art methodology to diagnose and stage soft tissue sarcomas in human patients, this technology hasn't been adopted yet in veterinary medicine. A common procedure for diagnosing the condition in dogs is the use of fine-needle aspiration. This helps a vet rule out other potential causes of a mass, such as a cyst.

Vets order a combination of lab tests with a biopsy before beginning any type of treatment in order to try to distinguish between the many types of soft tissue sarcomas.

Among the most common studies used to stage this type of tumor in dogs are blood and serum tests and radiologic imaging such as X-rays, CT scans or MRIs. Diagnostic tools like ultrasound are important to detect whether a soft tissue sarcoma has metastasized.

Treatment Options

A vet determines the most efficient treatment protocol for an affected dog based on the subtype of the tumor, where it's located, how large it is and how advanced the pet's disease is. Most vets refer a dog with soft tissue sarcoma to a veterinary oncologist, who develops the treatment plan.

Surgery is the treatment of choice for most dogs, with an emphasis on limb-sparing procedures. The initial surgery represents the dog's best chance to get all the tumor out of its body.

In cases where this is not possible or it's necessary to kill remaining malignant cells, radiation is used. When the soft tissue sarcoma appears not to be curable, this type of treatment can help control the tumor for an extended period of time and provide pain control.

Chemotherapy is sometimes effective in dogs with types of tumors that quickly metastasize. Specific types of soft tissue sarcoma respond to the use of chemotherapy after the dog has had surgery. Chemotherapy is usually reserved to the most aggressive and high-grade tumors and is seldom used as the only treatment.

Prognosis

Vets often act guarded when asked about the prognosis for soft tissue sarcoma in dogs. The objective of all treatment is local control of the tumor. Unfortunately, rates of recurrence vary so much - from 7 to 32 percent - that it's impossible for a vet to give a really meaningful number to an owner.

Overall, recurrences are harder to treat than initial tumors. The median survival time for dogs with soft tissue sarcoma is 1,416 days after surgery. Those who have undergone surgery followed by radiation live an average of 2,270 days.

Sources:

http://www.veterinarycancer.com/softtissuesarcoma.html

http://www.petcancercenter.org/Cancer_Types_soft_tissue_sarcoma.html