RET and breast cancer: Histopathological diagnostic thresholds for atypical hyperplasia (AH) and LCIS have changed over time.21 If some of the cases included in this study were in fact AH misclassified as LCIS, this could have contributed to our finding that IBIS-RET V7.2 overestimates BC risk, because AH confers a lower BC risk than LCIS.