A three-decade computer modeling study showed that up to 94% of papillary thyroid cancer (PTC) diagnoses detected by ultrasound were overdiagnosed. This phenomenon was mainly among women. The model estimated a high proportion of such cases over a long period. Overdiagnosis means finding tumors that would never cause problems. The article emphasizes that curbing such overdiagnosis is easier said than done. Study points to increasing incidence of PTC in association with improved detection.