# Ch11: Breast Imaging（乳腺影像）
Preparatory Mindset
Breast imaging is governed by age-based modality choice: mammography is the mainstay in women over 50; high-resolution ultrasound is the initial modality in women under 40; breast MRI is the most sensitive method of detecting breast cancer. The core skill is recognizing the mammographic signs of malignancy (spiculated mass, pleomorphic microcalcifications) vs benign findings (well-defined masses, coarse calcifications), and using BI-RADS to guide management.
Core Concepts
Modalities
- Mammography: low-dose X-ray of the breast using a dedicated X-ray machine (tungsten or molybdenum target, 40 KV soft X-ray). Standard views: craniocaudal (CC) and mediolateral oblique (MLO).
- Breast ultrasound: first-line in symptomatic women under 40 (breast tissues are dense; avoids irradiation); extremely useful for characterizing indeterminate mammographic findings; distinguishes cystic from solid; guides fine needle aspiration/biopsy.
- Breast MRI: most sensitive method of detecting breast cancer; depicts precise extent of malignant disease with very high sensitivity and moderate specificity; no ionizing radiation; accuracy unaffected by breast density; limitations: cost, access, not sensitive to calcification; dynamic enhancement very useful.
Key mammographic signs of breast cancer
- Ill-defined, irregular or spiculated mass or masses.
- Pleomorphic microcalcifications, often with a linear or ductal distribution, with or without an associated mass or soft tissue density.
- Associated features: architectural distortion, skin thickening, nipple retraction, axillary lymph node enlargement.
Benign vs malignant
| Feature | Benign | Malignant |
|---|---|---|
| Mass | Well-defined, ovoid/spherical | Ill-defined, irregular, spiculated |
| Calcification | Large and coarse | Pleomorphic microcalcifications (linear/ductal distribution) |
| US | Round/ovoid, well-defined borders, homogeneous internal echoes, absent or peripheral vascularity | Irregular, poorly defined, interrupts fascial planes, abnormal internal vascularity |
| MRI | Type 1 persistent enhancement | Type 2/3 washout curves |
| Associated | — | Architectural distortion, skin thickening, nipple retraction, axillary nodes |
Benign lesions
- Fibroadenoma: very well-defined hypoechoic ovoid mass on US.
- Benign masses: well defined, ovoid/spherical; may contain calcifications but generally large and coarse.
- Cysts: anechoic on US with posterior acoustic enhancement.
Malignant lesions on US
- Irregular spiculated heterogeneous mass; may contain hyperechoic microcalcification; intense (malignant) vascularity on Doppler interrogation.
Breast MRI enhancement curves (BI-RADS kinetics)
- Type 1 — persistent: signal intensity continues to rise (favors benign).
- Type 2 — plateau: rises then plateaus (indeterminate).
- Type 3 — washout: rises then falls (suspicious for malignancy).
- DCIS: linear and nodular enhancement typical of ductal carcinoma in situ.
BI-RADS (Breast Imaging Reporting and Data System)
- Standardized reporting: 0 incomplete, 1 negative, 2 benign, 3 probably benign (short-interval follow-up), 4 suspicious (biopsy), 5 highly suggestive of malignancy (biopsy), 6 known biopsy-proven malignancy.
- Used to standardize management; application is a familiarity item in the course.
High-Yield Points
- Key Point: Mammography >50 y; US <40 y; MRI = most sensitive for breast cancer.
- Key Point: Malignant = spiculated/irregular mass + pleomorphic microcalcifications + architectural distortion + skin thickening.
- Key Point: Benign = well-defined mass + large coarse calcifications.
- Key Point: MRI kinetics: persistent (type 1) benign; washout (type 3) malignant.
- Key Point: MRI is not sensitive to calcification; US is for young women and dense breasts.
- Key Point: BI-RADS 4 = suspicious (biopsy); 5 = highly suggestive (biopsy).
LMCHK OSCE Practice（OSCE & LMCHK）
- Breast mass is a listed LMCHK common case: describe the lesion (location, size, margins, calcification), state benign vs malignant features, and give the imaging pathway: under 40 → US; over 50 → mammography; MRI for extent in known cancer/high-risk screening.
- Mammographic breast cancer: spiculated mass + pleomorphic microcalcification + nipple retraction + axillary node — describe all associated features.
- Fibroadenoma (young woman) vs carcinoma (older woman): classic discriminator table.
- Know that US-guided biopsy confirms; MRI enhancement kinetics (persistent vs washout) guide further workup.
Topic Summary
Breast imaging uses age-based selection (mammography >50, US <40, MRI most sensitive). Malignancy is signaled by spiculated/irregular masses and pleomorphic ductal-distribution microcalcifications, with architectural distortion, skin thickening and nodal involvement; benign lesions are well-defined with coarse calcifications. US characterizes solid vs cystic and guides biopsy; MRI (dynamic enhancement curves: persistent vs washout) delineates extent and adds sensitivity; BI-RADS standardizes reporting (4/5 → biopsy).