Bone Biopsy
Bone Biopsy for Bone Cancer
There are two types of bone biopsy: open incisional biopsy and closed needle or trephine biopsy. The open method allows for removal of a good sized piece of tissue, which increases the chances of an accurate diagnosis. Bruising on the bone, wound infection, seeding of the surgical site with tumor cells and pathologic fractures are major disadvantages of this technique.
The closed needle (Jamshidi needle) or trephine (Michelle trephine) is preferred, since the incidence of post operative complications is greatly reduced. Even though it provides a smaller specimen, a quick, accurate diagnosis can be made in up to 94% of cases. There might be a slightly lower incidence of pathologic fractures with the Jamshidi needle.
In order to achieve the best results with biopsy, several specimens should be obtained. The biopsies should be taken from the center of the lesion, since bone cancer grows from the inside of the bone (medullary space) to the outside (cortex). If an open incisional biopsy is planned, the incision should be positioned so that the entire area can be completely removed if amputation is later scheduled.
The biopsy can be “negative” or “non-conclusive”. Reasons for this include:
- Sample was obtained from reactive bone
- Not enough samples were submitted
- The tumor is poorly differentiated and cannot be diagnosed on a small biopsy specimen
- There is necrosis of the bone
- The sample was crushed or squeezed during handling, or there was excessive decalcification of the bone specimen
Since the bone biopsy will not diagnose 100% of the cases, and most cases can be diagnosed and treated without a biopsy, there is really very little need for this invasive procedure. If the diagnosis is clear, and the dog is not a candidate for amputation because of other health problems, or because of the location of the tumor, then biopsies are not needed to determine an alternative cause of treatment. One must be prepared to amputate if there are complications from the biopsy, and the information needed from the specimen can be obtained after the amputation surgery.