Fibrosarcomas In Dogs

Tendons, ligaments and cartilage play various roles in connecting muscles, bones and other anatomical structures to each other. These connective tissues thus enable animals’ body movements such as walking and running. When a cancerous tumor originates in fibrous tissue such as these and others, it is called a soft tissue sarcoma. The most common soft tissue sarcoma is a fibrosarcoma. Fibrosarcoma in dogs is most likely to occur when they are older. Tumors can literally develop from head to toe, appearing anywhere from in the mouth or nose to the hind legs. Canine fibrosarcoma also can metastasize (spread), including to the lungs and lymph nodes. Fortunately, fibrosarcomas in dogs are treatable. As is the case with many other cancers, treatment is more likely to be successful if the cancer is caught early, so it’s important and helpful to always be on the lookout for suspicious lumps, bumps and inflamed areas.

Symptoms of Fibrosarcoma In Dogs

The signs of fibrosarcoma vary depending on the location of the tumor, its size and to what stage the cancer has advanced.

  • Oral fibrosarcoma in dogs typically presents as a mass in the mouth. Not all pet parents are in the habit of checking their dog’s mouth regularly but doing so can help catch a tumor early. A fibrosarcoma in a dog’s mouth also can result in oral bleeding, unexplained drooling and/or bad breath. Depending on the size of a fibrosarcoma and whether it is causing discomfort, a dog also may have trouble eating.
  • A fibrosarcoma in the nasal passages can obviously impact a dog’s breathing. This can manifest as sneezing, sounding congested, snorting and even snoring. Another symptom is nasal discharge, which may also be bloody.
  • Fibrosarcomas on other parts of a dog’s body typically present as a bump or lump. The soft tissue tumors also can grow in subcutaneous areas (beneath the skin), in which case the mass will be visible more as a bulge than a lump on the skin. They can develop anywhere, including the head and neck area and even between a dog’s toes. These are easily found by feeling, or petting, your dog.

Diagnosing Fibrosarcoma

If your dog has a suspicious lump or is exhibiting any other of the aforementioned symptoms, a trip to your veterinarian is in order. To determine whether cancer is present, a veterinarian typically will order full bloodwork, including a complete blood count (CBC) and chemistry profile, as well as a urinalysis. A tissue sample, retrieved through either a fine needle aspiration or biopsy/excision, if possible, is also needed so it can be sent to a lab for more detailed analysis. A CAT scan also can help assess the extent of the disease, especially for areas such as the nasal passages where the tumor can infiltrate into the sinuses as well. Getting a tissue sample is not always as easy in this area. A Rhinoscopy or an incisional biopsy may be needed in order to rule out the possibility of metastasis (spread) to the lungs, a chest X-ray should be ordered, as well.

Treatment and Prognosis for Fibrosarcoma Tumors in Dogs

Surgery and/or radiation are the treatments of choice for fibrosarcoma in dogs. The combination varies depending on a dog’s specific circumstances. There are occasions when treatment is curative. Other times, treatment is designed to improve your dog’s quality of life and extend your time together as much as possible. With fibrosarcoma, there is also the possibility the cancer eventually will return, even with treatment.

Treatment for Oral Fibrosarcoma

Aggressive treatment is typically indicated for an oral tumor. One option is debulking surgery, which is surgery designed to remove as much of the fibrosarcoma tumor as possible while sparing the underlying tissues. More aggressive, definitive surgery would involve taking out part of a dog’s jawbone to obtain wide margins. Unfortunately, this cancer tends to come back anywhere from a matter of weeks to months. Surgical debulking thus is often followed by radiation. There are two primary types of radiation — conventionally fractionated radiation therapy (CFRT) and stereotactic radiation (SRS). The latter is more innovative, using higher doses of radiation and precision targeting to fight the tumor. It typically requires fewer treatments (1 to 3, vs. 15 to 21 with CFRT) and thus significantly reduces the number of times a dog must be anesthetized. If surgery is ruled out for any reason, SRS can also be used as the primary treatment option. Successful radiation can extend your time with your dog for 6 to 18 months, with a good quality of life. If left untreated, an oral fibrosarcoma will continue to grow. Eventually, it will become difficult for a dog to eat, and his or her quality of life will decline. At that point, a pet parent may face a decision about euthanasia.

Treatment for Nasal Fibrosarcoma

Because of the location inside the nose, removal of the tumor can be exceedingly difficult and often of little benefit. As the goal is to achieve clean margins — meaning the outer edges of the removed portion are not cancerous, a good indication that all the cancer has been removed, this would be impossible with surgery. Radiation then becomes the gold standard go-to again, with SRS providing the benefit of fewer treatments and fewer anesthetic events. Treatment often extends a dog’s life by six to 18 months. An aftereffect worth noting is that during or weeks after treatment, a dog may experience postnasal drip, the result of dying cancer cells exiting the nasal passages.

Dog laying down on towel
Treatment for Fibrosarcoma Tumors on or Under the Skin

Depending on how a fibrosarcoma found on a dog’s body is graded (Grade 1, 2 or 3), there is a 10-25% percent chance of the cancer spreading to lymph nodes or the lungs. Surgery and/or radiation thus are the treatments of choice for these types of fibrosarcomas in dogs. The goal with surgery is to achieve margins of at least 3 centimeters around the mass. Otherwise, the cancer tends to come back in a matter of weeks to six months. Following surgery with radiation is sometimes curative. If surgery is ruled out or a pet parent opts against it, stereotactic radiation can be effective as a standalone treatment. There are also instances in which a mass is too large to remove and SRS is used first to reduce its size before surgery. If a pet parent opts to forego treatment entirely, a tumor will continue to grow. It’s worth nothing that Grade 1 and Grade 2 tumors grow very slowly, over the course of many, many months. Also know that tumors can grow quite large (think grapefruit-size) and become cumbersome even when they aren’t painful.

Chemotherapy for Fibrosarcoma

There have been some cases of canine fibrosarcoma that benefit from chemotherapy. While chemotherapy is not the mainstay of treatment, it has been shown to help slow subcutaneous tumors approximately 50% of the time for a period of months up to one year. Chemotherapy for this disease consists of pills typically given on every other day basis. Periodic visits to your veterinary medical oncologist would be needed to assess efficacy and for blood work to ensure that treatment is not affecting the body’s functions. For aggressive, grade 3 fibrosarcoma, your medical oncologist may recommend a combination of radiation coupled with chemotherapy in an attempt to treat your pet as thoroughly as possible. Please note, there is a moderate possibility that chemotherapy will be of little aid in this disease.

PetCure Oncology and Fibrosarcoma Treatment

PetCure Oncology treats fibrosarcoma in dogs, as well as other cancers. We offer a wide range of options and specialize in technologically advanced stereotactic radiation. Compassionate care is another component of our mission, which is to provide your pet the best quality of life while extending your time together as long as possible. For more information about our treatments and our mission, find a location near you and contact us today.

The contents of this article were provided in part by Dr. Renee Alsarraf, DVM, DACVIM (Oncology), a board-certified veterinary medical oncologist and member of PetCure Radiation Oncology Specialists (PROS).

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If your dog is displaying any symptoms of cancer or has been diagnosed with cancer, sort below by cancer type or tumor location to learn more about the most common types of cancer in dogs and available treatment options. Click on the links for more specific information on treatment and real patient stories.


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