I am 56 years old, 3 biopsies (october 2012 last one all benign), 2 sonohysterograms, hysteroscopy, ablation how likely is it that this is cancer?

Insufficient data: Your question can't easily be answered with the information you have given. I am guessing you have uterine bleeding to prompt all this evaluation. Biopsies can be negative if they miss a tumor, but 3 all negative if done by a competent gyn is unlikely to be a false negative, especially if all the other workup is negative. Still, it would depend on what other symptoms and if they persist..