Extremely dense breasts: A comprehensive review of increased cancer risk and supplementary screening methods

•About 10% of women have extremely dense breasts, doubling their breast cancer risk compared to those with non-dense breasts.•Mammography sensitivity drops with density. Tomosynthesis offers no improvement for extremely dense breasts; ultrasound boosts sensitivity but cuts specificity.•MRI improves cancer detection in women with extremely dense breasts, but high costs and limited availability may restrict its use.•Contrast-enhanced mammography matches MRI performance at lower costs, making it a viable option for extremely dense breast screening. Women with extremely dense breasts account for approximately 10% of the screening population and face an increased lifetime risk of developing breast cancer. At the same time, the sensitivity of mammography, the first-line screening modality, is significantly reduced in this breast density group, owing to the masking effect of the abundant fibroglandular tissue. Consequently, this population has garnered increasing scientific attention due to the unique diagnostic challenge they present. Several research initiatives have attempted to address this diagnostic challenge by incorporating supplemental imaging modalities such as ultrasound, MRI, and contrast-enhanced mammography. Each of these modalities offers different benefits as well as limitations, both clinically and practically, including considerations of availability and costs. The purpose of this article is to critically review the background, latest scientific evidence, and future directions for the use of the various supplemental screening techniques for women with extremely dense breasts.