Increasing trends in in situ breast cancer incidence in a region with no population-based mammographic screening program: results from Zurich, Switzerland 2003-2014.

BCIS ASR increased linearly over a 12-year period. The increase was reflected by an increase in DCIS ASR, whereas LCIS ASR decreased over time. The highest increase in BCIS ASR over the study period was observed for the < 40 year age group, even though not statistically significant. Patient and tumor characteristics of this group that may be associated with BCIS development warrant further investigation.