Treatment Options for Canine Fibrosarcoma

Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
I have a question regarding a diagnosis of fibrosarcoma in my 5-year-old Rottweiler. I searched your site on fibrosarcoma, but the only two cases discussed were both in the leg. My dog had a well-defined fibrosarcoma removed from the area of her sternum — the report indicated a low-grade malignancy and that the margins were healthy tissue. Given that information, and that it was on the torso and not a limb, would the prognosis be any different for treatment and possible recurrence? I plan to have her seen by a veterinary oncologist within a few days, but would like any statistical or general trends for this type of cancer and its treatment.

I would appreciate any information you can provide; she is a once in a lifetime dog, and I want to give her the best chance possible.

Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:

The treatment of choice for low-grade soft tissue sarcomas, which includes fibrosarcomas, is complete surgical excision with wide margins. The term "wide" is determined by the size and location of the primary tumor and to a lesser extent the number of prior surgeries. If both the surgeon and the pathologist are satisfied with the surgical margins, then surgery alone might be adequate. If there is any question about the adequacy of the surgical margins, either a wider surgical resection or radiation therapy might be recommended. These types of tumors are unlikely to metastasize; so local control of the tumor is the focus of treatment.

One additional comment on recurrence — the fact that a soft-tissue sarcoma might appear "well-defined" or "encapsulated" can be deceptive. These tumors can be surrounded by what appears to be a well-defined rim of fibrous tissue. In fact, this rim of tissue is actually composed of compressed tumor cells. Tendrils of the tumor may have extended beyond this rim. An analogy is a weed growing in the yard. The well-defined portion of the tumor can be thought of as the leaves above the ground, but what you can't see or feel is the root system underground. Remove just the leaves, and the weed can regrow from the roots that are left behind.

It is wise for you to discuss this case with a veterinary oncologist.