Exploring Dense Breast Density in Mammography: A Comparative Analysis of Breast Cancer Risk

Breast density is a strong predictor of breast cancer. However, the difference in risk between breast density categories C and D remains inadequately explored. Given the low occurrence of extremely dense breasts, this investigation is crucial because it may lead to modifications in screening techniques for those with these conditions.

The objective of the study is to evaluate the difference in breast cancer risk among women undergoing mammography and biopsy at a tertiary referral hospital in Colombia, based on American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) results in categories of breast density C (heterogeneously dense) and D (extremely dense).  Methods: This retrospective cross-sectional study recorded variables from the mammographic BI-RADS scale, as well as histological and clinical variables from digital medical records. A stratified analysis of lesion malignancy/benignity was conducted according to density category by mammography and histological findings. The association between mammographic breast density subclassification of dense breasts and the occurrence or not of pathology-defined malignancy was sought.  Results: A total of 107 patients with breast density in categories C and D were included, with 88.7% having heterogeneously dense breasts. The frequency of breast cancer was 32%. Infiltrating ductal carcinoma was the most frequently diagnosed malignancy (N = 14). A higher BI-RADS category was correlated with breast density grade D and malignancy. A statistically significant association (p <0.045, RR 1.95, CI: 1.12-3.50) was found when comparing breast density (categories C and D) with the risk of malignancy. The positive predictive value (PPV) varied across different BI-RADS categories (BI-RADS 4A 25% vs. 0%; p-value 0.005; BI-RADS 4B 50% vs 10.5%; p-value 0.032).

Efforts and resources should be focused on patients with extremely dense breasts, emphasizing the importance of additional (individualized) screening. Breast density could change the PPV within each BI-RADS category. However, further studies are needed to define the risk associated with each breast density subcategory and within BI-RADS categories, as well as to assess the efficacy of additional screening in patients with extremely dense breasts.