Hi
Welcome to the MedHelp forum!
Generally bone cysts are blood filled spaces separated by fibrous septa, especially after trauma. Other possibility is aneurismal bone cysts. Generally a CT scan is diagnostic. However, take a second opinion. Take care!
First, I recommend switching primary care physicians, as one who treats you for something you test negative for does not sound like a competent doctor.
Next, I'm surprised a foot doctor wants to biopsy for a fibula fracture, which is located above the foot. Does he specialize in ankles as well, if that's what part of the fibula he found the the break in? What diagnostic tests did he order that he is able to charactarize as cyst-like calcifications? Did he explain why he felt biopsy was warranted? If you are not comfortable with this surgery, I recommend you cancel until you can get a second opinion from perhaps an orthopedic surgeon.