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Soft Tissue Sarcoma in Dogs

What Is Soft Tissue Sarcoma in Dogs?

Soft tissue sarcoma (STS) in dogs refers to cancerous tumors that develop in the soft and connective tissues of their bodies. These tissues encompass muscles, nerves, tendons, blood vessels, and fat. While some soft tissue tumors may be benign, those classified as soft tissue sarcomas are malignant.

STS can manifest in various parts of a dog’s body since soft and connective tissues are widespread. However, the condition predominantly occurs in the skin and the layers of tissue beneath it. In fact, about 8 to 15% of tumors found in dogs in these areas are soft tissue sarcomas, and they tend to grow slowly over time.

Soft Tissue Sarcoma Grading

Soft tissue sarcoma tumors in dogs are categorized into three grades ranging from 1 to 3:

  • Grade 1 (low): The majority of soft tissue sarcomas in dogs fall into Grade 1. They typically exhibit minimal spread to other body areas and seldom invade neighboring tissues.
  • Grade 2 (intermediate): Grade 2 is the second most frequently diagnosed grade for soft tissue sarcoma in dogs. Similar to Grade 1, they usually do not metastasize or invade other parts of the body.
  • Grade 3 (high): Grade 3 soft tissue sarcoma accounts for only 7 to 17% of cases. These tumors have a higher likelihood of recurrence and metastasis compared to Grades 1 and 2, with metastasis occurring in 40 to 50% of diagnosed cases.

Staging involves evaluating three primary factors:

  • The degree of differentiation and behavior of cancerous cells compared to healthy cells.
  • The rate of cell division within the tumor, which indicates its growth rate.
  • The rate of cell death (apoptosis). While cell death is a natural process, cancerous cells often resist apoptosis, allowing the tumor to continue growing.


The symptoms of soft tissue sarcoma in dogs vary depending on the location of the tumor in their bodies. Here are some common manifestations:

  • Tumors originating from muscle tissue: Dogs may display signs of discomfort such as yelping or pulling away when the affected area is touched. Additionally, a visible and firm mass may be present.
  • Tumors located on the legs: These tumors can hinder movement, leading to limping or restricted mobility.
  • Abdominal tumors: Symptoms may include vomiting, diarrhea, weight loss, or reduced appetite.
  • Tumors arising from nervous tissue: Dogs may experience pain, lameness, muscle wasting, or paralysis.
  • Mouth tumors: Signs may include halitosis, difficulty eating, or decreased appetite.
  • Tumors affecting reproductive organs (e.g., the prostate): Dogs may have difficulty urinating or defecating.


The development of soft tissue sarcoma in dogs doesn’t have a single identified cause. Research indicates that various factors such as genetics, age, environment, hormones, body size, previous physical trauma, and chronic inflammation may contribute to its onset.

Certain dog breeds, particularly larger ones like the Airedale Terrier, Basset Hound, Bernese Mountain Dog, Boxer, Great Dane, and Saint Bernard, are more commonly diagnosed with soft tissue sarcoma.

Similar to many tumor types, older dogs are more prone to developing soft tissue sarcoma compared to younger ones.


Not all lumps and swellings are alarming, but it’s important to have them examined by your veterinarian. To ascertain whether a lump is indicative of soft tissue sarcoma, diagnostic tests are necessary. The most common test employed is fine needle aspiration (FNA), wherein a small needle with a syringe is inserted into the mass to extract a cell sample for microscopic examination.

If FNA results are inconclusive or if further clarification is required, a biopsy may be recommended. Biopsies are more invasive as they entail removing a portion of the tumor for analysis. This procedure provides additional insights into the tumor’s growth rate, stage, and optimal treatment approach. Typically, local anesthesia is administered to ensure your dog’s comfort during the biopsy.

Based on the findings, additional tests such as chest X-rays or abdominal ultrasounds may be advised to determine if the cancer has metastasized. Analysis of blood cells and specific chemicals in your dog’s blood, along with urine examination, may also be suggested. In certain cases, additional imaging techniques such as computed tomography (CT) scans may be warranted.


The treatment of soft tissue sarcoma in dogs depends on various factors including the type of tumor, its size and location, and your dog’s overall health. Your veterinarian will collaborate with you to devise the most suitable treatment strategy for your pet.

Surgery stands as the primary treatment for soft tissue sarcoma. It offers the highest likelihood of completely removing the tumor with minimal adverse effects and is the most cost-effective option in the long run. Grade 1 tumors typically respond well to surgery, with low recurrence rates if completely excised. Similarly, Grade 2 tumors often respond favorably to surgery, with reduced chances of recurrence if fully removed. Depending on the tumor’s location and grade, your veterinarian might refer you to a veterinary surgeon or oncologist to determine the optimal approach for your pet.

Soft tissue sarcomas possess tentacle-like extensions, making complete tumor removal challenging. Consequently, follow-up surgeries or radiation therapy may be necessary to ensure comprehensive tumor destruction.

In cases where surgery isn’t feasible due to tumor size or location, radiation therapy is often recommended. While radiation may not completely eradicate the tumor, it can impede its growth.

Chemotherapy may also be incorporated into your dog’s treatment plan, either independently or alongside surgery or radiation. It’s commonly advised for Grade III soft tissue sarcomas due to their increased propensity to metastasize to other body parts.

Recovery and Management

For Grade 1 or 2 soft tissue sarcoma, the prognosis following surgery is highly promising. Recurrence rates after surgery typically range from 7% to 30%, and they can be further reduced with the inclusion of radiation therapy and/or chemotherapy in the treatment plan.

Pet owners of dogs diagnosed with soft tissue sarcoma should schedule follow-up appointments for a minimum of two years post-surgery to monitor their pet’s condition and response to treatment.

Soft Tissue Sarcoma in Dogs FAQs

What is the prognosis for dogs with soft tissue sarcoma?

Dogs diagnosed with Grade 1 or 2 soft tissue sarcomas that are surgically removable generally have a favorable to excellent prognosis. However, Grade 3 soft tissue sarcomas have a more cautious prognosis.

Is soft tissue sarcoma painful for dogs?

Soft tissue sarcoma typically isn’t painful. Since soft tissue sarcomas are often detected early due to their visible presence, treatment options are available. However, advanced soft tissue sarcomas located near the skin surface may cause discomfort if the skin breaks open.

How quickly does soft tissue sarcoma progress in dogs?

Soft tissue sarcomas generally progress slowly, although some may develop within a few weeks. Soft tissue sarcomas of lower grades are less likely to metastasize to other body parts.

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