Breast cancer screening is a critical NP competency requiring understanding of breast cancer biology, screening test characteristics, risk assessment models, and evidence-based guideline recommendations. Breast cancer biology relevant to screening: Breast cancer develops from ductal or lobular epithelial cells through a progression: normal epithelium to atypical hyperplasia to carcinoma in situ (DCIS/LCIS) to invasive carcinoma. DCIS (ductal carcinoma in situ) is a non-invasive precursor that may or may not progress to invasive cancer — it is primarily detected by mammography as microcalcifications and represents approximately 20-25% of mammographically detected cancers. The overdiagnosis debate centers largely on DCIS: some DCIS lesions would never progress to clinical cancer during the patient's lifetime, yet once detected, most are treated with surgery and radiation. Invasive ductal carcinoma (IDC) accounts for 70-80% of invasive breast cancers, while invasive lobular carcinoma (ILC) accounts for 10-15% and is more difficult to detect mammographically because it grows in single-file infiltrating patterns rather than forming a discrete mass. Mammography principles: Standard 2D mammography uses low-dose X-rays to image compressed breast tissue, detecting masses, microcalcifications, and architectural distortion. Digital breast...