Soft Tissue Sarcoma in Dogs: Treatment, Causes & Prevention (Vet Answer) – 33rdsquare

Soft Tissue Sarcomas in Dogs: A Comprehensive Guide

Hello friend, let‘s have an important discussion about a type of cancer that can affect our beloved canine companions – soft tissue sarcomas. As a dog lover and veterinarian, I want to equip you with the knowledge to catch these tumors early and pursue the best treatment options for your pup. While soft tissue sarcomas can be serious, I have seen many dogs do well with prompt, appropriate care. So let‘s dive in and learn more about this complex disease.

What are soft tissue sarcomas?

Soft tissue sarcomas are a group of malignant tumors that arise from the connective tissues of the body. This includes fat, muscle, cartilage, tendons, ligaments, joint capsules, blood vessels, and nerves. So while they are often found in the skin and subcutaneous tissue, soft tissue sarcomas can develop anywhere in the body. In dogs, common sites include the limbs, trunk, and oral cavity.

Soft tissue sarcomas are relatively rare, accounting for 15% of all skin and subcutaneous tumors in dogs. However, they are locally aggressive. The tumor cells invade surrounding normal tissue, often in finger-like projections. This makes it challenging to completely remove the tumor surgically. Distant spread (metastasis) is less common, occurring in about 15-25% of cases depending on the tumor type and grade.

Types of soft tissue sarcomas in dogs include:

• Fibrosarcoma – arise from fibrous connective tissue
• Peripheral nerve sheath tumor – arise from the cells that surround and support nerves
• Hemangiopericytoma – arise from cells surrounding small blood vessels
• Liposarcoma – arise from fat cells
• Myxosarcoma – arise from connective tissue that produces a mucus-like substance
• Undifferentiated sarcoma – lack microscopic characteristics of a specific cell type

What causes soft tissue sarcomas in dogs?

Like most cancers, the exact cause of soft tissue sarcomas in an individual dog is usually unknown. A complex mix of genetic and environmental factors likely contribute to abnormal cell growth and tumor development over time.

Certain risk factors are known to increase a dog‘s chances of developing soft tissue sarcomas:

• Breed – large breeds are overrepresented. Golden retrievers, Labrador retrievers, German shepherds, Bernese mountain dogs, and Brittany spaniels appear to be at higher risk.

• Age – middle-aged to older dogs (median age of 10 years)

• Genetics – some studies suggest a hereditary component in Flat-coated retrievers and Bernese mountain dogs

• Chronic inflammation – sarcomas can arise at sites of previous trauma, surgical implants, or injections (especially vaccines)

The role of environmental carcinogens (cancer-causing substances) is unclear. Further research in canine sarcomas is needed.

What are the signs of soft tissue sarcomas in dogs?

Soft tissue sarcomas often appear as firm, subcutaneous (under the skin) masses that are not painful. However, signs vary depending on tumor location and which tissues are involved:

• Skin/subcutaneous – slow-growing lumps under the skin. Usually not painful or irritating. May see redness, hair loss, or ulceration.

• Mouth – swelling, bad breath, drooling, difficulty eating, loose teeth

• Gastrointestinal tract – vomiting, diarrhea, loss of appetite, weight loss, black tarry stools

• Bones/joints – lameness, limping, swelling of limbs

• Nose – nasal discharge, nosebleeds, facial deformity, difficulty breathing

• Spleen – lethargy, pale gums, collapse, distended abdomen

Many of these signs are non-specific and can indicate other health issues. See your veterinarian right away for any new lump or concerning symptoms. Early diagnosis allows for timely treatment and better outcomes.

How are soft tissue sarcomas diagnosed?

Obtaining a definitive diagnosis is critical for determining treatment and prognosis. Your veterinarian will begin with a thorough physical exam and medical history. Be sure to point out any lumps you have found on your dog.

The initial test is usually a fine needle aspirate. This quick, non-invasive procedure involves inserting a thin needle into the mass and extracting some cells. The cells are examined under a microscope by a veterinary pathologist. Fine needle aspirates can often diagnose a sarcoma but may not identify the specific subtype.

For a more definitive diagnosis, a biopsy is needed. An incisional biopsy removes just a small portion of the tumor, while an excisional biopsy removes the entire mass. Biopsies require sedation or anesthesia. The tissue sample is processed and analyzed microscopically. The pathologist will grade the tumor (low, intermediate, or high) based on how abnormal the cells look. Higher grade tumors tend to be more aggressive.

Additional diagnostic tests help determine the extent of disease and guide treatment:

• Bloodwork to assess organ function and check for paraneoplastic syndromes
• Chest x-rays to look for lung metastasis
• Abdominal ultrasound to evaluate internal organs for spread and rule out other causes of symptoms
• Advanced imaging (CT or MRI), especially for hard to access locations like the mouth, spine, or pelvis

What are the treatment options for soft tissue sarcomas?

Treatment of soft tissue sarcomas depends on the tumor location, size, grade, and whether it has metastasized.

Surgery is the mainstay of treatment for localized soft tissue sarcomas. The goal is to completely remove the tumor along with a wide rim of normal tissue. This can be challenging due to the tumor‘s tendency to spread along tissue planes. In some cases, amputation of a limb may be necessary. For tumors that cannot be completely excised, a second surgery may be recommended 2-3 weeks later.

Radiation therapy uses high-energy beams to damage and kill cancer cells. It may be recommended for sarcomas in locations that limit the ability to achieve wide surgical margins, like the mouth or spine. Radiation can also be given after surgery if tumor cells remain (dirty margins). The protocols vary but usually involve daily treatments for 3-4 weeks.

Chemotherapy is less effective for sarcomas compared to other cancers. It is generally reserved for high-grade tumors or those that have spread to other areas of the body. The most common drug is doxorubicin, given intravenously every 2-3 weeks. Chemotherapy does not cure sarcomas but may slow progression and provide some survival benefit.

There are some newer, targeted therapy drugs in development and clinical trials for canine sarcomas, like toceranib and masitinib. These oral medications work by blocking receptors on the tumor cells that drive growth. They may be an option if conventional treatments are declined or not possible. Ask your veterinarian or a veterinary oncologist about clinical trial opportunities.

Regardless of the therapies chosen, all dogs should receive appropriate pain control and supportive care. This may include oral pain medications, special diets, physical therapy, and complementary therapies like acupuncture and supplements. Work closely with your vet to keep your dog as comfortable as possible and maintain a good quality of life.

What is the prognosis for dogs with soft tissue sarcomas?

The prognosis for dogs with soft tissue sarcomas depends on several tumor and patient factors:

• Grade – Low and intermediate grade sarcomas that can be completely excised have a good prognosis. High grade sarcomas tend to be more invasive and likely to spread.

• Location – Sarcomas on the limbs have a better prognosis than those on the trunk. Tumors in the mouth tend to have a guarded prognosis.

• Ability to achieve wide surgical margins – Dogs with completely excised (clean margin) sarcomas live significantly longer than those with incomplete excision (dirty margins).

• Presence of metastasis – Prognosis is guarded to poor for dogs with distant spread. The lungs are the most common site of metastasis.

• Response to radiation – Dogs that have a complete response to radiation tend to do better.

• Overall health – Older dogs with other health issues may be more prone to complications or side effects from treatments.

Specific survival times vary but one large study of 687 dogs with various soft tissue sarcomas found:
• Median survival time (50% alive) of 1416 days with surgery alone
• 2270 days with surgery and radiation
• Only 236 days if the tumor was not removed

Keep in mind these are averages and an individual dog may do better or worse. In general, about 60% of dogs with low to intermediate grade soft tissue sarcomas that are completely removed will survive 3 years. While more guarded, dogs with high grade or incompletely excised tumors may still benefit from surgery plus radiation with median survival times around 1-3 years.

Early detection and treatment is key for the best prognosis. At home, be proactive about checking your dog for any new lumps or bumps. Run your hands along their body once a month and make note of any growths. Have your vet check any suspicioius masses right away. Catching sarcomas when small and localized greatly improves treatment success.

If faced with a sarcoma diagnosis, I know it can feel overwhelming. Take the time to fully discuss all the options with your veterinarian. Do not hesitate to seek a second opinion or consultation with a veterinary oncologist. They can provide more details on your dog‘s specific case as well as latest research and clinical trials. Consider reaching out to support groups for pet cancer. Speaking with others who have gone through a similar challenging situation can be a wonderful source of encouragement and advice.

While the journey with canine cancer is never easy, there is hope. With prompt appropriate treatment and a dedicated support team, many dogs with soft tissue sarcomas can maintain an excellent quality of life. As both a veterinarian and dog lover, I will be cheering you on every step of the way.