Screening, Diagnosis, and Staging
Screening
Mammography is the backbone of average-risk screening, and major guidelines differ on start age and interval; know the thresholds used at your institution and the rationale behind them. Digital breast tomosynthesis improves detection in dense tissue. Breast MRI is reserved for high-risk groups, typically a lifetime risk of about 20-25% or more, known mutation carriers, and prior chest radiation.
Diagnosis
The workup is triple assessment: clinical examination, imaging, and tissue sampling. BI-RADS categories guide next steps: 0 incomplete, 1 negative, 2 benign, 3 probably benign with short-interval follow-up, 4 suspicious (biopsy), 5 highly suggestive of malignancy, 6 known biopsy-proven cancer. Core needle biopsy is preferred over fine-needle aspiration because it preserves architecture and allows receptor testing. Every invasive cancer needs estrogen receptor, progesterone receptor, and HER2 testing; HER2 is scored by immunohistochemistry, with 2+ requiring in situ hybridization.
Staging
Staging uses the TNM system. Stage IV is any T, any N, with distant metastasis. Inflammatory breast cancer is T4d and at least stage III unless metastatic. Sentinel lymph node biopsy is standard for a clinically node-negative axilla; completion axillary dissection is now used selectively.
Traps
Excisional biopsy as a first step, biopsying a BI-RADS 3 lesion, treating HER2 2+ as positive without reflex testing, and ordering CT, PET, or bone scans in asymptomatic early-stage disease. Staging imaging is driven by symptoms, laboratory findings, or clinical stage.
Rule of thumb. If the question describes a suspicious finding, the answer is image-guided core biopsy, not watchful waiting.