Updated: May 3
Cancer is common in dogs, with almost half of dogs over ten years old developing some form of the disease before the end of their lives. Among the many different forms that cancer can take is sarcoma, which itself has many forms.
Let's look deeper into canine sarcoma and learn what we can.
What is Sarcoma?
Sarcoma is a name for a type of cancer occurring in the connective tissues of a body. The name comes from Greek with the root word Sarx, meaning "flesh," because it's one of the most fundamental elements of the body that this cancer comes from.
Connective tissues appear all throughout the body and can be found everywhere, from the bones and joints to the lining of blood vessels and nerve sheaths. It can also occur in other forms of soft tissue, including fat cells, tendons, cartilage, and ligaments.
What are the Different Types of Canine Sarcoma?
There are as many different names for subtypes of sarcoma as there are tissues that can develop the disease.
They're generally differentiated using the medical prefix for whatever that tissue is. For example:
Osteosarcoma is sarcoma in the bones (osteo = bone)
Liposarcoma is sarcoma in the fat cells (lipo = fat)
Hemangiosarcoma is sarcoma in the blood vessels (hema = blood and angio = vessel)
Some of the most common forms of sarcoma in dogs include osteosarcoma, STS or Soft Tissue Sarcoma, and hemangiosarcoma. Other forms of sarcoma are less common or are lumped generally under the Soft Tissue Sarcoma banner because most of them behave similarly enough and respond to similar treatments such that they aren't useful to draw a distinction between them in a clinical or casual setting.
How is Canine Sarcoma Diagnosed
Sarcoma in dogs usually presents in two ways.
The first is by a lump that either the pet owner or the vet examining the animal can see or feel under the skin. In extreme cases, the tumor may put enough pressure on the skin that it breaks open or ulcerates, but more commonly, it's just an unidentified lump under the skin that needs diagnosis to identify.
The second is due to symptoms. For example, a hemangiosarcoma can grow unnoticed for months or years within a dog until one day, it bursts and causes an immediate crisis requiring emergency veterinary care. In other cases, a growing sarcoma on a bone, ligament, or joint can hinder mobility and cause numbness or pain that the pet owner notices and brings their dog in for evaluation.
How is Canine Sarcoma Identified
When a lump or tumor is discovered in a dog, the first step to identification is typically a fine needle aspiration. Fine needle aspirations use a very small needle inserted into the tumor to extract some small amount of cells or fluid as relevant and send that sample off for testing.
Fine needle aspirations are fast and relatively painless, but they are less accurate than surgical biopsies. In a biopsy, a larger needle or probe is used to remove a larger sample of a tumor or, in cases where the tumor is small or located in an area where it's not dangerous to remove, the whole tumor can be removed surgically. This sample is sent to a lab for evaluation and testing.
The first step in the lab for either kind of sample is to identify what, exactly, they're looking at.
This is done using an examination of the cells on a microscopic level. From there, if the sample is identified as cancerous, further examination can lead to staging.
Further examination can involve a CT scan to image the body and look for additional tumors and other disruptions. This further aids staging and can inform treatment options.
Is Canine Sarcoma Curable?
Some forms of canine sarcoma are small, localized, and minimally aggressive. These tumors can be removed surgically, and subsequent treatments can help prevent their return.
Other forms of canine sarcoma are much more aggressive or may have already spread or metastasized throughout the body. This is a significant risk with some kinds of sarcoma – like hemangiosarcoma – because they grow internally and show no outward signs until they have already grown to a point where they are dangerous or have spread.
"Soft tissue sarcomas are very invasive into the surrounding normal tissue, and the tumor is usually larger than what is visible or palpable. As a group, these tumors have a relatively low metastasis rate to other organs, but this rate is dependent on the histologic grade of the tumor. Grade I and II tumors have a less than 20% chance of spreading. Grade III tumors metastasize in about 40-50% of patients." – Blue Pearl Vet.
One of the most difficult aspects of cancer is that one must be extremely thorough in treatment, which typically means large margins in surgical excision, as well as systemic drugs and other treatments. This is because cancerous cells replicate themselves, so if even a small handful of cells survive a treatment, the cancer can return.
Further, many sarcomas are very locally invasive; the observable boundaries of the tumor may be significantly smaller than the extension of cancerous cells into surrounding tissues. This makes surgical removal alone a difficult option to recommend.
Is Canine Sarcoma Preventable?
No cancer is truly preventable. The trouble with cancer is that it's nothing more than a mutation of the DNA of a cell in the body, causing that cell to replicate its own broken self aggressively.
That mutation can be caused by a wide range of different things, from exposure to radiation to carcinogenic chemicals like tobacco smoke or alcohol to stray cosmic rays or some infections.
Genetic factors and predispositions also play a role, which is very pronounced in dogs with variance between different breeds and their likelihood of developing certain cancers. Beyond that, cancer is relatively poorly understood as a whole, and there are hundreds of versions of it, all with their own distinct qualities.
While some actions and lifestyle changes can be made to reduce the chances of developing cancer, there's no way to prevent it entirely. Vigilance and proactive monitoring can help diagnose cancers before they become problems and keep them more treatable, however.
What are the Treatment Options for Canine Sarcoma?
There are four general treatment options for sarcomas in dogs.
"Pretty much every cancer has treatment options, and that ranges from curative surgery to palliative therapies where we keep them comfortable for long periods. Some tumors aren't resectable, or surgery is probably not going to remove cancer, but it's slow-growing, and we can keep them comfortable for a very long time." – Animal Hospital of Statesville.
The first is surgical resection. Surgical removal of a tumor is usually the first option for most tumors. Canine sarcomas are often isolated and solitary except when they're in advanced stages, so a surgical removal can get rid of cancer and have a reasonable chance of it not coming back.
That said, surgical removal requires large margins for sarcomas due to their aggressive spread.
This, combined with their basis in connective tissue, means that some forms of sarcoma cannot be easily surgically removed. Sometimes sarcoma can grow on critical organs or on joints means they would be deadly or debilitating to remove as a whole.
A second option is radiation therapy. Radiation is used to kill cells in a targeted area and can be used to target tumors that can't be fully removed surgically. Often, radiation is used either pre-operative or post-operative, with surgery still part of the treatment plan.
Other types of radiation therapy include radiation used as the sole treatment option, usually on tumors that can't be surgically removed at all. Additionally, radiation can be used as palliative care to stall the growth of a tumor and extend life without the detriment to the quality of life (and risk) that comes with chemotherapy and surgery.
Palliative radiation reduces the pain and inflammation associated with an aggressive or otherwise untreatable tumor but isn't a cure.
Chemotherapy is the third major treatment option for canine sarcomas and other cancers. Chemotherapy drugs operate on a variety of different channels and can do things like attack specific cancer cells or attack the method cancer uses to build its blood vessels and prevent it from feeding itself.
Chemotherapy drugs are also the most thorough and useful means of treating cancers that have spread or are high-grade and have a significant risk of spreading. Unlike human chemotherapy, canine chemotherapy often has relatively little, if any, side effects.
Finally, novel and advanced treatment options are being developed every year, piggybacking off developments in human cancer treatment. The greatest recent developments include targeted drugs and immunotherapy stemming from genetic testing of cancer samples. Companies like FidoCure and Vidium offer these genetic evaluations and provide recommended treatment options.
"The patient's overall health status plays a major role in therapy choices for dogs with cancer. This includes evaluating the patient for his or her ability to tolerate cancer treatment. Life expectancy should be taken into consideration as well; for a slow-growing tumor in an older dog, for example, treatment drawbacks may outweigh potential benefits." – Lombard Veterinary Hospital.
Results can vary for these treatment options depending on details such as the dog's breed, age, staging, the cancer type and location, and more. Every case is individual and unique, making cancer very difficult to treat with boilerplate protocols.
What's the Prognosis Like for Canine Sarcoma?
The prognosis depends entirely on the staging of the cancer, its location, and other factors relating to its treatability.
The smaller, more superficial, and the earlier the tumor is noticed, the more likely it is that the cancer is curable and long-term outlooks are good. In many cases, when caught early, cancer can be fully removed with little or no chance of it returning.
As tumors grow larger, or if they're located in sensitive areas that can't be fully removed (like on organs, the spine, or in the mouth), they become harder to treat and more likely to recur. While the use of targeted chemotherapy and even immunotherapy can be effective, there's a greater chance of cancer returning in these cases.
Once a tumor has spread, it's almost guaranteed to come back after treatment. Often, treatment can extend the life of a dog by 9-15 months, and sometimes more, but once cancer has reached an advanced enough stage, it's only a matter of months, not years.
In cases where treatment isn't an option for either financial or health-related reasons, palliative care can give a dog a few extra weeks or months with a higher quality of life.
As a Vet, What Can You Do?
As a vet, you want to give your patients the best possible outcomes, regardless of circumstances.
Short of becoming a canine oncologist yourself, the next best thing you can do is keep one on call. We're here to help provide that service for you.
Cancers can be very complex, and it's not always easy or even possible to know what the right move is when you're not an oncology specialist yourself. By calling our service, we can advise you on the best next steps for a given patient. You don't have to rely on impartial, boilerplate treatment plans and can instead get specific options for a specific patient's specific cancer. This can mean the difference between palliative care and successful treatment.
Cancer isn't the only thing we do, either. At Hope Vet, we provide consulting services for oncology, neurology, complex internal medicine cases, emergency and critical care, and dermatology.
Moreover, we can help you as a vet handle some of the stresses and struggles of being the bearer of bad news. You don't have to go it alone; we can provide the support you need to provide the best possible service and outcomes for your patients.
We encourage you to contact us today to learn what services we can provide for you! Please give us an email at firstname.lastname@example.org or give us a call at 253-341-5835 and we'll respond to you as soon as possible.