Which Tumors This Page Covers 

The word sarcoma appears in the names of several very different diseases, and landing on the wrong page is easy.

This page covers the tumors that behave as a group: fibrosarcoma, perivascular wall tumor, peripheral nerve sheath tumor, myxosarcoma, liposarcoma, and undifferentiated sarcoma, among others. If your dog's pathology report names one of these, you are in the right place.

These are different diseases with their own pages:

• Hemangiosarcoma arises from blood vessel lining and spreads far more readily
• Osteosarcoma arises in bone and behaves aggressively
• Histiocytic sarcoma is considerably more aggressive than the tumors described here

If you are unsure which group your dog's tumor belongs to, the pathology report will name it specifically. Ask your veterinarian to confirm which category applies, because the outlooks are not comparable.

What Soft Tissue Sarcomas Are 

Connective tissue is the body's structural material: the fibrous tissue, fat, nerve sheaths, and vessel walls that hold everything else in place. It exists throughout the body, which is why these tumors can appear almost anywhere, though limbs and the trunk are most common.

They account for roughly 15 percent of skin and subcutaneous tumors in dogs. Most dogs are diagnosed at around nine or ten years of age. Larger breeds are affected more often, including Golden Retrievers, Labrador Retrievers, Boxers, Bernese Mountain Dogs, and Saint Bernards.

Nothing about diet, exercise, or care causes them.

Why They Behave the Way They Do

This is the concept that explains every treatment decision on this page, and it is worth understanding properly.

A soft tissue sarcoma looks and feels well contained. On examination, and even during surgery, it often appears to be a discrete mass sitting inside a smooth capsule, as though it could be lifted out cleanly.

That appearance is misleading. What looks like a capsule is compressed normal tissue with tumor cells growing through and beyond it. The tumor sends microscopic extensions outward into surrounding tissue, invisible to the eye and impossible to feel, sometimes reaching a considerable distance from the visible edge.

The practical consequence is direct: removing only what can be seen leaves tumor cells behind, and those cells regrow. This is why a soft tissue sarcoma that was "shelled out" often returns at the same site months later, larger and harder to remove the second time, because it is now growing through scar tissue.

The counterpart is equally true. A tumor removed with an adequate margin of normal tissue around and beneath it frequently never comes back at all.

If your dog has a mass that might be a soft tissue sarcoma, the most valuable thing you can do is ensure the first surgery is planned as a cancer surgery rather than a lump removal.

Signs to Look For 

Soft tissue sarcomas usually present simply as a mass.

• A firm or rubbery lump, on or under the skin
• Slow growth, often over months, sometimes years
• Usually not painful and often not bothering the dog at all
• May feel fixed to underlying tissue, or fairly moveable
• Can become quite large before anyone becomes concerned

Because they grow slowly and cause no discomfort, these tumors are frequently watched for a long time before being investigated. That is the most common way treatment gets harder than it needed to be.

Tumors arising from nerve sheaths can cause additional signs: persistent lameness, muscle wasting in a limb, or weakness, sometimes before any mass can be felt. A dog with unexplained progressive lameness and muscle loss in one leg warrants investigation.

Any lump that is new, growing, or has been present without explanation should be sampled rather than monitored by appearance.

How Soft Tissue Sarcomas Are Diagnosed 

Expect this to take longer than you might hope, and understand why.

Fine needle aspiration frequently does not give an answer. Connective tissue tumors shed cells poorly, so aspirates often come back inconclusive, or reported as a population of spindle cells that could be several things. This is a limitation of the tumor type, not a failure of your veterinarian or the laboratory.

This is a meaningful difference from mast cell tumors, where aspiration usually settles the question quickly. With a suspected soft tissue sarcoma, an inconclusive aspirate is a common and expected step.

Biopsy is usually needed. Taking a small piece of tissue provides a definitive diagnosis and, importantly, a grade before surgery. Knowing the grade in advance allows the surgery to be planned appropriately.

Advanced imaging with CT or MRI is valuable for larger tumors, tumors on limbs, and any tumor near important structures. It shows the true extent of the mass and helps the surgeon plan margins. For a substantial tumor, this is worth asking about.

Staging includes chest X-rays to check for spread, and assessment of nearby lymph nodes. Because distant spread is uncommon for low and intermediate grade tumors, staging is usually less extensive than for cancers that spread readily.

What Grade Means

Soft tissue sarcomas are graded from I to III based on how the cells look, how rapidly they are dividing, and how much dead tissue is present within the tumor.

Grade I tumors spread only rarely, in well under ten percent of cases. Complete removal is usually the whole treatment, and the outlook is excellent.

Grade II tumors carry a modest risk of spread. Local control remains the main focus.

Grade III tumors are more serious, with spread occurring in a substantial minority of dogs; commonly estimated at around 40 to 50 percent. These warrant discussion of treatment beyond surgery.

Most soft tissue sarcomas are Grade I or II.

The report may also list a mitotic count, measuring how quickly cells are dividing. Like grade, a higher count is associated with a worse outlook, and it is worth asking your veterinarian what your dog's number means.

The report will also describe margins; whether the tumor was removed completely, narrowly, or incompletely. For this cancer, that single line is often the most important thing on the page.

Treatment

Surgery

Wide surgical removal is the primary treatment and, for most low and intermediate grade tumors, the only treatment needed.

The surgeon removes a margin of normal-appearing tissue around the tumor and a layer of tissue beneath it, to capture the microscopic extensions described above. The traditional standard was three centimetres in each direction; current evidence supports somewhat narrower margins in many cases. Either way, the incision will be considerably larger than the lump, which surprises many families.

Location determines how achievable this is. Tumors on the trunk usually have spare tissue available. Tumors on a lower limb often do not, and achieving adequate margins there can require reconstructive techniques or, occasionally, amputation.

Complete removal of a low-grade soft tissue sarcoma results in recurrence in only a small minority of dogs. Incomplete removal results in regrowth in a substantially higher proportion. That difference is why planning matters.

Radiation

Radiation is highly effective for tumor cells left behind after incomplete removal, and it is the standard recommendation in that situation. Dogs treated with radiation after an incomplete excision frequently go years without recurrence.

It is also used when a tumor cannot be removed adequately because of its location, either to shrink it before surgery or as the primary treatment.

If your dog's report says incomplete margins, radiation is the conversation to have.

A second surgery

Where enough tissue remains, removing more of the surgical site is an alternative to radiation after incomplete excision. This is more difficult than the first operation, because the surgeon is now working through scar tissue without a visible tumor to guide them, but it is often effective and may be more practical than travelling to a radiation facility.

Chemotherapy

Chemotherapy has a more limited role here than in many cancers, and it is worth being honest about the evidence.

For high-grade tumors and for dogs with confirmed spread, doxorubicin-based chemotherapy is generally recommended. For low and intermediate grade tumors that have been removed completely, there is little evidence that adding chemotherapy improves outcomes, and it is usually not advised.

Metronomic chemotherapy — low doses given continuously as tablets at home, typically combining an oral chemotherapy drug with an anti-inflammatory — has evidence supporting its use for delaying recurrence after incomplete removal of a soft tissue sarcoma. It is well tolerated and inexpensive relative to conventional protocols. Ask about it if complete removal was not achieved and radiation is not an option.

Amputation

For some limb tumors, particularly larger ones or those that have already recurred, amputation may offer the best chance of permanent local control. Dogs adapt to limb loss far better than most families expect. Our page on osteosarcoma discusses amputation recovery in detail.

Integrative and supportive care

Standard supportive care applies: protecting the surgical site while it heals, managing pain, and keeping your dog eating and comfortable.

Be cautious with supplements around surgery, since fish oil and turmeric at higher doses affect clotting. If your dog is receiving radiation, discuss any antioxidant supplements with your oncologist specifically, since there is unresolved debate about whether they interfere with treatment.

No supplement, herb, or diet has been shown to treat soft tissue sarcoma in dogs. 

Comfort Care Alone

For an older dog with other serious conditions, or where a tumor has become extensive, comfort-focused care is a legitimate path. Because these tumors are often slow-growing and not painful in themselves, some dogs live comfortably with an untreated mass for a considerable period. The issues that eventually arise are usually mechanical; a mass interfering with movement, or ulcerating through the skin.

Discuss with your veterinarian what to expect for your dog's specific tumor and location.

What Treatment is Actually Like For Your Dog

Surgery is the usual experience. Expect an incision much larger than the lump, ten to fourteen days of restricted activity, and a recovery collar or surgical suit. Where a large amount of tissue was removed, a drain may be placed for a few days and healing may take longer. Most dogs are comfortable within days on pain medication and return to normal activity within a few weeks.

Radiation, when needed, is a series of brief sessions under light anaesthesia, typically daily or several times weekly over some weeks. The treated skin becomes red and irritated much like sunburn, and heals over several weeks afterward. Most dogs tolerate the sessions themselves without difficulty.

Metronomic chemotherapy is tablets at home with periodic bloodwork and urine checks. Most dogs show no visible side effects.

Conventional chemotherapy for dogs is dosed for quality of life rather than for eliminating the disease at any cost. Most dogs experience no significant side effects, and most do not lose their coat.

Understanding Prognosis

For most dogs with a soft tissue sarcoma, the outlook is good.

Low and intermediate grade tumors removed completely carry an excellent prognosis. Recurrence is uncommon, distant spread is uncommon, and many of these dogs are permanently free of the disease and live a normal life span.

Incompletely removed low or intermediate grade tumors recur in a meaningful proportion of dogs, but radiation or a second surgery substantially improves control, and long disease-free periods are the usual result.

High-grade tumors are more serious, with spread occurring in a substantial minority and shorter median survival. Treatment beyond surgery is generally recommended.

The pattern worth holding onto is that for this cancer, local control is usually the battle. Unlike most cancers on this site, the question is more often will it come back here than has it spread everywhere, and that is a considerably more winnable fight.

What It Costs

Costs vary by region and practice type. Ask for a written estimate.

• Aspiration and cytology: approximately $150 to $400, though frequently inconclusive for this tumor type
• Biopsy: approximately $400 to $1,000
• CT or MRI for surgical planning: approximately $1,500 to $3,000
• Surgical removal: approximately $1,000 to $4,000, depending on size, location, and whether reconstruction is needed
• Histopathology: approximately $150 to $400
• Radiation: approximately $4,000 to $8,000
• Metronomic chemotherapy: relatively inexpensive, typically modest monthly cost plus monitoring
• Conventional chemotherapy: approximately $2,000 to $5,000

Spending on proper planning before surgery — imaging, a biopsy for grade — often costs less than a second operation and radiation afterward. Our page on paying for cancer treatment lists sources of help.

Living with It Day to Day

After recovery, most dogs return entirely to normal.

Check the surgical site regularly. Recurrence, when it happens, appears as a new firm swelling at or near the scar, usually months later. Run your fingers over the area monthly and report any thickening promptly, because a small recurrence is far more manageable than a large one.

Check the rest of your dog too. Some dogs develop more than one soft tissue sarcoma over their lifetime, and any new lump should be sampled rather than watched.

Report to your veterinary team: any new or returning lump, swelling at the surgical site, lameness or muscle wasting in a limb, or coughing and reduced stamina, which can indicate spread.

Recheck schedules are usually based on grade. For high-grade tumors, periodic chest X-rays are typical.

Questions Worth Asking Your Veterinarian

• What specific type of sarcoma is this, and does it behave like the group described here?
• What grade is it, and what was the mitotic count?
• Were the margins complete? If not, what are our options?
• Would imaging before surgery help plan the margins?
• Is this a surgery my regular practice should do, or should we see a surgical specialist?
• If we cannot achieve clean margins, is radiation available, and is metronomic chemotherapy an option?
• What is the realistic chance of this coming back?
• How often should we recheck, and what should I feel for at home?

Thinking About Quality of Life

For most dogs on this page, this section will not apply. A low or intermediate grade sarcoma removed completely is a solved problem, and relief is the appropriate response.

For dogs with high-grade tumors, spread, or a tumor that cannot be removed, quality of life becomes the guiding measure. Watch comfort, appetite, mobility, engagement with the family, and whether good days still outnumber bad. Tumors that ulcerate through the skin require attentive wound care and are a common reason quality of life declines, so raise this with your veterinary team if it begins.

If treatment stops working, ask your care team what to expect and what the plan should be. Having that conversation early is easier than having it in crisis.

Common Questions

Is soft tissue sarcoma likely to spread? For low and intermediate grade tumors, which are the majority, spread is uncommon. High-grade tumors spread in a substantial minority of cases. The more common problem with this cancer is regrowth at the original site rather than spread to distant organs.

Why does the incision have to be so much bigger than the lump? Because these tumors send microscopic extensions into surrounding tissue well beyond their visible edge. Removing only what can be seen leaves cells behind that regrow. The wide margin is what makes the removal permanent.

The needle sample did not give an answer. Is that a problem? It is common and expected. Connective tissue tumors shed cells poorly, so aspirates are frequently inconclusive. A biopsy is usually the next step and provides both a diagnosis and a grade.

The margins were incomplete. What happens now? This is a common situation with a good solution. Radiation to the site achieves excellent long-term control, and a second surgery is an alternative where enough tissue remains. Metronomic chemotherapy is another option. Recurrence is not inevitable, and it is not immediate.

Can a soft tissue sarcoma be removed for good? Frequently, yes. A low or intermediate grade tumor removed with complete margins often never returns, and those dogs commonly live out a normal life span.

My dog's lump has been there for a year without changing. Does that mean it is benign? Not necessarily. Soft tissue sarcomas are often slow growing and cause no discomfort, so a long-standing unchanged lump can still be one. Any lump that has not been sampled should be, regardless of how long it has been there.

Does my dog need chemotherapy? Usually not. For low and intermediate grade tumors removed completely, there is little evidence that chemotherapy improves outcomes and it is generally not recommended. It is advised for high-grade tumors and for dogs with confirmed spread.

This page is for education and does not replace advice from your own veterinarian, who knows your dog. Any new or growing lump should be examined and sampled rather than monitored by appearance alone.