The increased incidence is not likely to be due to environmental or therapeutic radiation because the percentage of RET/PTC rearrangements decreased..     ///    The proportion of RET/PTC rearrangements decreased from 11% to 2% (P = .038).     ///    "We identified and histologically reviewed 469 consecutive cases of PTC from one US institution from 4 preselected periods (1974 to 1985, 1990 to 1992, 2000, and 2009) and assessed BRAF and RAS point mutations and RET/PTC rearrangements among 341 tumors ?0.3 cm in size. "