Breast Disease & Breast Cancer
A high-yield board review of breast disease from benign lesions through breast cancer — pathophysiology, classic vignette buzzwords, age-based workup, current screening, and next-best-step management calibrated for Step 1 and Step 2 CK.
Overview & the board approach
Breast cancer is the most common non-skin cancer in women and the second-leading cause of cancer death in women (after lung). Most breast complaints — a lump, pain, or nipple discharge — are benign, but every dominant or persistent mass must be worked up to exclude malignancy. The unifying risk theme is lifetime estrogen exposure: early menarche, late menopause, nulliparity, late first pregnancy, obesity (postmenopausal), and hormone therapy all raise risk; the strongest non-modifiable factors are increasing age, female sex, and germline BRCA1/BRCA2. Evaluation follows triple assessment — clinical exam, imaging (mammography ± ultrasound), and tissue biopsy (core needle preferred) — with imaging choice driven by age. Two reflexes earn points: (1) a normal mammogram never rules out a palpable cancer, so a suspicious mass still needs ultrasound and biopsy; and (2) most cancers are invasive ductal carcinoma presenting as a hard, fixed, irregular mass, classically in the upper-outer quadrant.
- Fibroadenoma — most common benign tumor in women <30; firm, rubbery, mobile ("breast mouse"); estrogen-responsive (enlarges in pregnancy); negligible malignant potential.
- Fibrocystic change — most common cause of lumps ages 20–50; cyclic, bilateral pain and nodularity, worse premenstrually.
- Simple cyst — fluctuant; anechoic and well-defined on US; aspirate if symptomatic.
- Intraductal papilloma — most common cause of bloody/serosanguineous nipple discharge; small subareolar single-duct lesion.
- Fat necrosis — after trauma/surgery/radiation; firm irregular mass that mimics cancer; oil cyst/dystrophic calcification on mammo.
- Duct ectasia — periareolar green-brown discharge in older/smoking women.
- Lactational mastitis — S. aureus; tender, erythematous, febrile; treat with continued breastfeeding + dicloxacillin/cephalexin; fluctuance → drain abscess.
- Phyllodes tumor — large, fast-growing, "leaf-like"; needs wide local excision with clear margins (can be malignant; spreads hematogenously, so nodes are usually spared).
Benign lesions at a glance
| Lesion | Classic clue | Key point / next step |
|---|---|---|
| Fibroadenoma | Young woman, mobile rubbery mass | US first; observe or excise if large/growing |
| Fibrocystic change | Cyclic bilateral lumpy pain | Reassure; NSAIDs, supportive bra |
| Simple cyst | Fluctuant, anechoic on US | Aspirate if symptomatic; biopsy if bloody or residual mass |
| Intraductal papilloma | Bloody unilateral single-duct discharge | Mammo/US + duct excision |
| Fat necrosis | Trauma/surgery, mimics cancer | Biopsy to exclude malignancy |
| Phyllodes tumor | Large, rapidly enlarging | Wide local excision (nodes usually spared) |
- In situ (no basement-membrane invasion):
- DCIS — true precursor; microcalcifications on mammo; comedo subtype has central necrosis. Treat with excision ± radiation.
- LCIS — a risk marker (bilateral risk), not a mass or obligate precursor; E-cadherin negative; surveillance ± risk reduction.
- Invasive:
- Invasive ductal carcinoma (IDC) — most common (~75%); hard, stellate, gritty.
- Invasive lobular carcinoma — single-file cells, loss of E-cadherin; often bilateral/multifocal.
- Inflammatory — peau d'orange, erythema; dermal lymphatic invasion; NOT an infection; poor prognosis.
- Paget disease — eczematous, scaly nipple; overlies underlying DCIS/carcinoma.
- Receptors drive therapy: ER/PR+ → endocrine therapy; HER2+ → trastuzumab; triple-negative (ER−/PR−/HER2−) → chemo, worse prognosis, associated with BRCA1.
Vignette: A 22-year-old woman notes a 1.5 cm, firm, non-tender, freely mobile, rubbery mass in the upper-outer left breast. No skin change, discharge, or lymphadenopathy.
Diagnosis: Fibroadenoma.
Next best step: Ultrasound — first-line imaging under ~30 because dense breast tissue limits mammography. A well-circumscribed, homogeneous solid mass supports fibroadenoma. Confirm with core needle biopsy if imaging is suspicious or the lesion is large/growing; otherwise a classic, biopsy-concordant fibroadenoma can be monitored. Excise if >2–3 cm, enlarging, or symptomatic.
Vignette: A 58-year-old woman has 3 weeks of a red, warm, swollen, tender right breast with peau d'orange (orange-peel dimpling). She is not lactating, is afebrile, and a 10-day antibiotic course did nothing.
Diagnosis: Inflammatory breast cancer (dermal lymphatic invasion) — not mastitis.
Next best step: Diagnostic mammogram/ultrasound plus skin punch and core biopsy. A non-lactating woman whose "breast infection" fails antibiotics needs biopsy, not more antibiotics. Treatment is neoadjuvant chemotherapy → modified radical mastectomy → radiation; breast conservation is contraindicated. It is at least stage III (T4d) with poor prognosis.
Endocrine therapy: Tamoxifen vs. Aromatase inhibitor
| Feature | Tamoxifen (SERM) | Aromatase inhibitor (anastrozole/letrozole) |
|---|---|---|
| Mechanism | Blocks ER in breast | Blocks peripheral estrogen synthesis |
| Population | Pre- or postmenopausal | Postmenopausal only |
| Bone | Agonist in bone → protective (postmenopausal) | Osteoporosis ↑ |
| Uterus / clots | Endometrial cancer & VTE risk (agonist) | No endometrial/VTE excess |
| Other | Hot flashes, cataracts | Arthralgias, hot flashes |
- Palpable mass by age:
- <30: ultrasound first; add mammogram/biopsy if suspicious.
- ≥30: diagnostic mammogram + targeted ultrasound, then core needle biopsy (preferred over FNA — distinguishes invasive from in situ and gives receptor status).
- Reflex: a negative mammogram does not exclude a palpable cancer → proceed to US ± biopsy.
- Simple cyst: reassure/aspirate; bloody aspirate or residual mass → biopsy.
- Screening (average risk, USPSTF 2024): biennial mammography ages 40–74. BRCA carriers / prior chest radiation: add MRI and start earlier.
- Surgery: breast-conserving therapy (lumpectomy + whole-breast radiation) equals mastectomy in survival. Sentinel lymph node biopsy for clinically node-negative disease.
- Adjuvant: endocrine therapy (ER+), trastuzumab (HER2+; monitor cardiotoxicity/↓EF), chemo (triple-negative/high-risk).
- Peau d'orange + red breast, no fever → inflammatory breast cancer (dermal lymphatic invasion)
- Single-file ("Indian-file") cells + loss of E-cadherin → invasive lobular carcinoma
- Bloody, single-duct nipple discharge → intraductal papilloma
- Scaly, eczematous nipple → Paget disease of the breast
- Mobile "breast mouse" in a young woman → fibroadenoma
- New mass after trauma with calcifications → fat necrosis
- Microcalcifications on screening mammogram → DCIS
- Tamoxifen memory hook: blocks estrogen in the breast, but is an agonist in bone and uterus (→ endometrial cancer / VTE risk)
Practice Reproductive now
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