Poorly Differentiated Sarcoma

Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
Our 11-year-old miniature schnauzer recently had a biopsy to remove a mass on his front leg. The diagnosis was: "Poorly differentiated sarcoma, possible fibrosarcoma". The veterinarian has recommended amputation as quickly as possible. This seems so radical since the report was "possible fibrosarcoma". If we decide against amputation, what would be the advisable alternatives and their potential for success?

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

I'd like to clarify the interpretation of the biospy results. As written, they indicate that the mass is definitely a kind of cancer called a sarcoma. The "possible fibrosarcoma" means that while it is definitely a sarcoma, it is difficult to determine what type of sarcoma, and that fibrosarcoma is the pathologist's best guess. In general, poorly differentiated tumors mean that the tumor cells are so malignant that it is impossible to determine the normal tissue type from which the tumor is derived. This is a poor prognostic indicator because poorly differentiated tumors are more likely to be locally aggressive and to metastasize (that is, spread elsewhere in the body) than are well-differentiated tumors.

Before any treatment is undertaken, it is advisable to evaluate the regional lymph nodes (by at least fine needle aspiration and cytology). Chest X-rays are also advisable to look for evidence of tumor spread. Amputation is the best option for local control of the tumor, particularly if it is large. A second option would be surgical "debulking" IF this is possible followed by radiation therapy to eliminate residual cancer cells. The benefit of adding chemotherapy to the treatments listed above is unknown at this time.

If you or your veterinarian have not already done so, please consult a qualified veterinary oncologist to further explore the treatment options for your pet.