Pretty much the same thing happened to me. Originally my thyroid was "precancerous", so it was removed. Then, 25 years later a largish growth came back. In spite of multiple biopsies, the cancer wasn't identified until after surgery. It's Hurthle Cell, which isn't always identified by the biopsies. I did I131 radiation, which doesn't do much for HCC, but hey why not! Now, 2 years later, a nodule grew back. It was surgically removed, along with some lymph nodes. PET scan came back clear. I'm about to start external beam radiation to hopefully kill any remaining little Hurthle cells. It's going to be rough, but I'm glad I'm doing it. HCC is fairly aggressive. What kind of cancer do you have?