Accuracy of Fine Needle Aspirate in Sarcoma Diagnosis

Lili Duda, VMD
Last Modified: November 1, 2001

Dear OncoLink "Ask the Experts,"
Our 10-year old neutered mixed-terrier was diagnosed with sarcoma of the front left elbow by x-rays and a fine-needle aspirate. He then had chest x-rays (which showed no evidence of macroscopic pulmonary metastasis), and a biopsy, including a bone sample. However, the biopsy results were negative in all specimens, including the bone. Our specialist gave us two choices:

  1. amputate the leg now with the possible knowledge that we are amputating a leg with no cancer, or  
  2. wait one month and then re-x-ray the leg and chest with possible biopsy of the same area
We have chosen option two, knowing that in one month the cancer could metastasize and it could be too late to save our dog.

Is there anything else we could be doing now to possibly save the life of our dog? Would it help to take a blood sample? We feel we are wasting valuable time if he does have cancer.  
Feeling helpless,

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

Fine-needle aspirates can be difficult to interpret, particularly in the presence of inflammation. Fine-needle aspirates are rarely definitively diagnostic. Rather, they are usually "suggestive" or "compatible with", and this is why your veterinarian wanted to confirm the diagnosis with a biopsy before doing a more radical procedure such as an amputation. You are in a difficult situation, and it is hard to wait when you are worried cancer is present. However, it has been almost a month since your dog's last tests, so it might be a good time to repeat the diagnostics again with your veterinary specialist — X-rays to see if there have been any changes in the bone since his last examination, and more biopsies of the bone and soft tissues. These two tests are probably the best two tests that are readily available (there are no blood tests that can diagnose bone cancer).

There are some other tests that may or may not be appropriate for your dog and they are only available at some larger veterinary hospitals. These tests are a CT or MRI scan, and a nuclear scintigraphy scan. Please ask your veterinary specialist for more information about these tests and whether they might help.