RET and thyroid gland carcinoma: However, in a study of thyroid nodules in individuals with no history of radiation exposure, Belarusian subjects exposed to post Chernobyl radioactive fallout and individuals exposed to external irradiation of head and neck, Elisei et al. (2001) have indicated that the presence of RET/PTC rearrangements in thyroid cancer was not higher in radiation induced tumors compared with those naturally occurring [35].