Thyroid cancer is cancer of the thyroid gland. The thyroid concentrates iodine and so is extremely sensitive to the effects of various radioactive isotopes of iodine produced by nuclear fission. These radioactive isotopes increase the chances of developing cancer, though thyroid cancer can develop even without any exposure to radioactivity. There are several types of thyroid cancer and treatment depends on cell type: it can include surgery and destruction of thyroid cells by radioactive iodine.