Canine Soft-Tissue Sarcomas in Dogs

Adrienne is a certified dog trainer and former veterinarian assistant who
partners with some of the best veterinarians worldwide.

Soft-Tissue Sarcomas in Dogs

Fabian Gieske

Canine Cancer: Diagnosis, Treatment, and Life Expectancy

You might not have heard about soft-tissue sarcomas in dogs until your vet
pronounced these words. Whether your vet suspects or confirms a soft-tissue
sarcoma in your dog, you will likely have many questions. A great number of
pet owners aren’t aware of the many conditions that dogs can develop, and vet
visits often don’t leave much time for questions, so it’s quite common to
resort to the internet to learn more.

This article is the summation of my research on this topic. You can learn a
lot online as long as you rely on reputable websites, and the sources in this
article will bring you to websites that you may find useful. Researching your
dog’s medical condition lets you know what to expect and what follow-up
questions to ask at your next appointment.

Malignant Soft Tissue Sarcoma

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What Are Soft-Tissue Sarcomas in Dogs?

You may be aware that medical terms that end in “oma” often suggest nothing
good. Indeed, the word “sarcoma” comes from the following Greek words:

sarx , meaning flesh
oma , meaning growth

So a soft-tissue sarcoma, as its name implies, is simply a fleshy growth found
in the dog’s soft tissues like fat, muscle, nerves, fibrous tissues, blood
vessels, and the deeper skin tissues.

Where Are They Found?

These tumors are found on connective tissues, which consist of the material
that holds your dog’s body structures together. As such, they can be present
in any part of the dog’s body.

Sarcomas account for about 15% of all the skin tumors affecting dogs,
according to veterinary cancer experts. They are commonly found in middle-aged
dogs as solitary masses and go ignored for a long period of time; some can
grow quickly. Large dog breeds are commonly predisposed to them and male dogs
appear to be more likely to get them.

Traits of Soft-Tissue Sarcomas

Originate as pseudo-capsules
Develop poorly defined margins
Characterized by finger-like projections that infiltrate between muscles and layers of connective tissues

Do They Metastasize?

When you touch these growths, they may be easily movable, or more commonly,
they may be fixed in place—well attached to underlying tissues as if they had
roots. These tumors are generally considered minimally invasive, meaning that
they are unlikely to metastasize. It is quite uncommon that they spread to the
bone.

In the occasional event that they do metastasize, their preferred sites
include the lungs, followed by the lymph nodes. These tumors are usually not
painful but can be irritating and interfere with movement when they get large.
However, just because they are minimally invasive doesn’t mean they aren’t
serious. Soft-tissue sarcomas, when left untreated, can have a big impact on
the quality of a dog’s life.

Types of Soft-Tissue Cancer

Sarcomas are given different names depending on the type of tissue affected.
The following are some subcategories of soft-tissue sarcomas:

Hemangiosarcoma: originating from the blood vessels
Fibrosarcoma: originating from fibrous tissue
Liposarcoma: originating from fat
Lymphangiosarcoma: originating from the lymph vessels
Leiomyosarcoma : originating from smooth muscle
Peripheral nerve sheath tumor : originating from nervous tissue
Rhabdomyosarcoma: originating from skeletal muscle
Synovial Sarcoma : originating from connective tissue lining the cavities of joints and tendon sheaths

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Unfortunately, They Are Difficult to Diagnose

It’s not uncommon for your vet to be unsure about your dog’s diagnosis. Truth
is, things can get tricky when looking for signs that confirm a sarcoma. When
your vet does a fine-needle aspirate, the results may come back inconclusive,
and therefore, the diagnosis may come back as non-diagnostic. This is because
soft tissue sarcomas do not exfoliate well. That means they are reluctant to
release cells from the mass for evaluation. Some vets will try to get a better
sample by using a larger gauge needle (such as an 18 or 20 gauge).

How Are They Graded?

Sarcoma cells often appear as spindle-shaped cells with wide bodies and
tapered ends. The Merck Veterinary Manual describes these “spindle-cell”
sarcomas as “shaped like an octopus, with tentacles that extend deeply into
the tumor bed.” Yet, if the fine needle sample is inconclusive, surgical
excision with biopsy is often recommended as there is more mass to evaluate.

When biopsied, the pathologist will grade the sarcoma with a grade of 1, 2, or
3, or low, intermediate, or high. Under the microscope, the pathologist looks
at several factors such as the amount of dividing cells, the percentage of
dying cells, and how similar the cells are to the normal ones. The grading of
the sarcoma will ultimately play a big role in prognosis and treatment.

Several Treatment Methods Exist For Sarcomas.

Allie Smith

Prognosis and Treatment in Dogs

According to the National Canine Cancer Foundation, sarcomas that are more
than five centimeters in diameter don’t respond to chemotherapy or radiation
therapy. Generally, the larger and deeper the tumor, the more likely it is to
cause trouble. A rapidly growing tumor is also a much greater concern than a
slowly growing one, according to the Merck Veterinary Manual.

Will My Dog Survive?

A dog’s prognosis is based on several factors, keeping in consideration the
grading of the sarcoma. Generally, lower-grade tumors have a better chance of
being minimally invasive; whereas higher-grade tumors have a greater chance of
regrowing and spreading. According to Vet Surgery Central, metastasis tends to
occur at 5 to 10 percent in grade 1 tumors; up to 25 percent in grade 2
tumors; and up to 50 percent in grade 3 tumors.

Risk of Metastasis Based on Grade

Vet Surgery Central

Rating| Chance of Metastasis
—|—

Grade 1

5 to 10%

Grade 2

<25%

Grade 3

<50%

When Is Surgery Indicated?

Olga Kononenko

Will My Dog Need Surgery?

When these tumors are located in areas where there is ample loose skin,
removal may be easy. However, often sarcomas grow in areas where skin is
tight, such as the lower limbs or head. Aggressive surgery with wide margins
is often needed. Complete removal may be difficult in some areas and the roots
of the tumor may be left behind which leads to a recurrence.

Complications With Treatment

A lack of skin structure due to previous excision may cause the tumor to
become open and difficult to remove again surgically. In other cases, tumors
grow so much that the skin overlapping the tumor splits, leading to an ugly,
ulcerating, open wound. When this happens, radiation therapy or even
amputation of the limb may be necessary. It’s a good idea to have the surgery
done by a veterinary surgeon specializing in oncology. (Kim A. Selting, DVM,
MS, DACVIM, oncology, offers several tips on the surgical procedure.)

How Long Will My Dog Live?

According to Robyn Elmslie, a veterinarian specializing in oncology, the
average survival time in dogs diagnosed with an intermediate to low-grade soft
tissue sarcoma who undergo surgery along with radiation therapy is often
greater than six years. If you are looking for success rates with surgical
removal, consider local tumor recurrence rates after surgery. Whether
accompanied by radiation or not, these success rates tend to range from 7 to
32 percent, according to Pet Cancer Center.

This article is accurate and true to the best of the author’s knowledge. It
is not meant to substitute for diagnosis, prognosis, treatment, prescription,
or formal and individualized advice from a veterinary medical professional.
Animals exhibiting signs and symptoms of distress should be seen by a
veterinarian immediately.

Comments

Adrienne Farricelli (author) on October 16, 2018:

This is interesting, hopefully more and more vets will want to give this
product a try.

Everett D Heard on September 30, 2018:

Isopet, cures sarcoma in animals. It will be huge! RDGL (radio gel) .02 pps

Devika Primić from Dubrovnik, Croatia on August 27, 2014:

Informative and very helpful.

clivewilliams on August 27, 2014:

Good information