Breast Imaging
Core concepts
Master the BI-RADS lexicon and categories: 0 (incomplete), 1 (negative), 2 (benign), 3 (probably benign, short-interval follow-up), 4 (suspicious, biopsy), 5 (highly suggestive of malignancy), 6 (known malignancy). Understand mammographic signs: masses (shape, margin, density), calcifications (benign: coarse, round, vascular; suspicious: pleomorphic, linear, branching), architectural distortion, and asymmetry. Know the role of ultrasound (simple cyst vs solid mass; suspicious features: irregular shape, nonparallel orientation, spiculated margins, shadowing) and MRI (high sensitivity, used for screening in high-risk patients). Recognize the appearance of DCIS (linear/branching calcifications) and invasive carcinoma (spiculated mass).
Traps
Do not call calcifications benign without assessing morphology and distribution. Beware the negative mammogram in dense breasts-supplemental ultrasound or MRI may be needed. A category 3 lesion is not a biopsy; a category 4 lesion is. Do not confuse a fibroadenoma (well-circumscribed, oval, parallel) with a malignancy.
Rule of thumb
Suspicious calcifications are pleomorphic, linear, or branching; benign calcifications are coarse, round, or vascular.
Worked example
A screening mammogram shows a cluster of linear branching calcifications in one quadrant: BI-RADS 4 or 5, requiring stereotactic biopsy to evaluate for DCIS.