Histopathological features of breast cancer from 2005 to 2019 in a single center in Croatia: an overview of changes following the introduction of mammography screening

INTRODUCTION: Croatia launched the National program for the early detection of breast cancer (BC) in 2006. The program targets women between the age of 50 and 69 to take a mammogram every two years. About 60% of women performed mammography through the program. The study aimed to determine the difference in breast cancer’s pathohistologic features before and after the introduction of screening. MATERIALS AND METHODS: Data was collected retrospectively in a single high volume center for women diagnosed with invasive BC in the period before the introduction of mammography screening (2005-2007; N=1833), and from newly diagnosed (2017-2019; N=2676). Statistical significance of the findings was evaluated using Chi square test. RESULTS: We recorded a 31.5% increase in the number of patients referred to our hospital in the post-screening period. However, no statistically significant reduction in tumor size, histological grade or the number of positive axillary lymph nodes was detected in newly diagnosed BC compared to those diagnosed over ten years ago. The mean age of BC incidence was 61 years, with the mean tumor size of 22 mm (median 18 mm), in both periods. The significant difference occurred in the distribution of the intrinsic subtypes of BC (P<.001). About 45% of patients were diagnosed with pT1N0 stage, in both periods. CONCLUSION: In the post-screening period, we treated 32% more newly diagnosed breast cancers. However, pathohistological features of BC, along with the average tumor size, did not change.