|What is skin fibrosarcoma?
Skin fibrosarcoma is a common sub-type of tumors in both cats and dogs known as soft tissue sarcomas. Soft tissue
sarcomas is a general term that refers to a group of tumors that form in tissues of mesenchymal origin such as the
connective tissue (e.g. fat, smooth muscle, blood vessels, lymph vessels, skeletal muscle, etc). In dogs, fibrosarcomas are
most common on the trunk and extremities. In cats, the administration of vaccines (e.g. rabies and feline leukemia virus) is
associated with an increased risk of fibrosarcoma at the site of vaccination (for more information, visit the Vaccine-
associated Fibrosarcoma in Cats section).
How is fibrosarcoma diagnosed in cats and dogs?
Soft tissue sarcomas can be challenging to distinguish from each other as well as from other types of tumors due to the
overlapping features and patterns. In human medicine, new tools became available (e.g. immunocytochemistry, tissue
microarrays) that have helped pathologists to better diagnose soft tissue sarcomas but their application in veterinary
medicine is still rather limited. Prior to initiating any type of treatment, it is important to gather as much information as
possible regarding the tumor's tissue origin, size, site, histologic grade (level of aggressiveness) and whether it has
spread to other organs.
Fine-needle aspirates are recommended to exclude other possible causes of suspected mass (e.g. abscesses, cysts, or
mast cell tumors), however, cytologic evaluation by itself is usually not sufficient to reach a definitive diagnosis, and a
biopsy prior to initiating any type of treatment should be done. There are a variety of different biopsy techniques that can
be used but excisional biopsy is usually not recommended since surgery is typically performed after confirming diagnosis,
and multiple surgical attempts have a negative impact on survival for soft tissue sarcomas. Additional tests such as blood
and serum biochemical tests, chest X-rays and imaging are performed in order to evaluate how advanced the disease is.
Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role
in educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets
is to prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.
To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the Cancer Pain Management section.
Is nutritional support important for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for
example, some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).
Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need
to be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more,
please visit the Cancer Nutrition section.
What are the treatment options for skin fibrosarcoma in cats and dogs?
Wide and deep surgical removal of the tumor is the treatment of choice for fibrosarcomas, but because most practitioners
underestimate how much tissue should be removed, the tumor comes back in over 70% of the cases within 1 year of the
initial surgery. The rate of recurrence (coming back) is over 90% for vaccine-associated sarcomas. Radiation therapy can
be used after surgery to prevent the tumor from growing back at its original site. Chemotherapy with drugs such as
carboplatin, doxorubicin and cyclophosphamide, or dacarbazine has been recommended for tumors that cannot be
surgically removed and/or to prevent cancer cells from forming new tumors at other distant sites. Immunotherapy is a
novel type of treatment and there is some evidence that administration of a biologic response modifier (a molecule that
interacts with the immune system) before surgery and followed by radiation therapy can provide better outcome for the
Where do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist in your area who can discuss with you appropriate cancer treatment plan for
your pet's cancer condition, please visit the "Locate a veterinary oncologist" section.
Are there any clinical trials investigating new treatments for skin fibrosarcoma in cats and dogs?
There are several clinical trials ongoing for dogs with soft tissue sarcomas in pets, which are partially funded by the
institutions. To learn more about these trials, please visit the Clinical Trials for Soft Tissue Sarcoma in Dogs section.
Additionally, there are several clinical trials available for cats and dogs with any tumor type for which your pet may qualify.
To learn more these trials (which are partially or fully funded by the institutions), please visit the Dog Clinical Trials (any
tumor type) or Cat Clinical Trials (any tumor type) section.
To learn more about veterinary clinical trials in general, please visit the Pet Clinical Trials section.
What is the prognosis for skin fibrosarcoma in cats and dogs?
The prognosis for soft tissue sarcoma is good. Local control of the tumor is very challenging and local tumor recurrence
(tumor coming back) rates after surgery (with or without radiation therapy) range from 7% to 32%. Poor prognostic factors
for local tumor recurrence include large tumor size, incomplete surgical removal and high histologic tumor grade (high
grade corresponds with aggressive tumor behavior). Management of recurrent soft tissue sarcomas is usually more
difficult than the original tumor, emphasizing the need for an aggressive treatment of the initial tumor. Because the
median time for tumor recurrence is 368 days, the pets should undergo long term follow up and frequent check ups. The
metastatic rate for soft tissue sarcomas varies from 8% to 17% with a median time to metastasis of 1 year, depending on
the tumor's properties. The median survival time for dogs with soft tissue sarcoma is 1416 days with surgical treatment
and 2270 days with surgical and radiation treatment.
Additional online resources about fibrosarcoma in cats and dogs
|Skin Fibrosarcoma in Cats and Dogs
|PET CANCER CENTER
Comprehensive guide to cancer diagnosis and treatment in cats and dogs