Breast Anatomy, Physiology, and Pathology
What the exam tests
This domain tests normal breast structure, hormonal physiology, lymphatic drainage, and the imaging appearances of benign and malignant disease. Expect questions that link anatomy to where cancers arise and how pathology appears on mammography.
Core concepts
- Surface and support: breast quadrants, upper outer quadrant and tail of Spence, nipple-areolar complex with Montgomery glands, skin, and Cooper suspensory ligaments.
- Functional unit: the terminal duct lobular unit (TDLU) is the milk-producing lobule plus terminal duct; most breast cancers arise here.
- Lymphatic drainage: predominantly to axillary lymph nodes, with some drainage to internal mammary nodes.
- Physiology: cyclic hormonal changes, pregnancy and lactation, and menopause with fatty replacement and decreasing density.
- Pathology: benign lesions include cysts, fibroadenomas, papillomas, fat necrosis, and abscess; malignant disease includes DCIS, invasive ductal and lobular carcinoma, inflammatory carcinoma, and Paget disease.
- Imaging signs: masses, calcifications, architectural distortion, asymmetry, skin thickening, and nipple retraction.
Traps
- The upper outer quadrant is the most common cancer site, but cancer can occur anywhere.
- Most cancers arise in the TDLU, not the nipple.
- Fibroadenoma is common in younger women; cysts are common in women in their 30s to 50s; both can feel like lumps.
- Inflammatory carcinoma may present with erythema and peau d'orange without a discrete mass; biopsy is required.
- Not all calcifications are malignant; morphology and distribution matter.
Worked example
A 38-year-old presents with a smooth, mobile mass. Fibroadenoma and cyst are both considerations; ultrasound is typically the next step to distinguish cystic from solid.