Breast Anatomy and Sonography

Breast Anatomy and Sonography

• The breast is a modified sweat gland, primarily functioning to secrete milk for lactation.
• It sits anterior to the pectoralis muscle and ribs, lateral to the sternum, and medial to the axilla.

Breast Anatomy

• Breast tissue size varies based on age, functional state, and individual tissue amount.
• Puberty and pregnancy increase tissue size due to estrogen.
• Post-menopause, tissue decreases (atrophy) with often fatty replacement.
• Breasts consist of 4-20 lobes of parenchymal tissue and supporting tissue (fat, fibrous connective tissue).
• Lobes are made up of lobules and ducts, and small branch ducts.

Functional Unit of the Breast

• The Terminal DuctoLobular Unit (TDLU) is the origin site of most breast pathologies and cancers.
• It contains lobules, ductules, intralobular terminal ducts, fibrous tissue (stroma), and extralobular terminal ducts.
• Most breast carcinomas emerge from terminal ducts near the junction of the intralobular and extralobular segments.

Ducts and Sinuses

• Smaller ducts combine to form larger ducts, ultimately becoming lactiferous ducts.
• These ducts may function as milk reservoirs.
• Normal duct size is less than 2 mm and can be sonographically visualized.

Breast Zones

• Pre-mammary zone (AKA Subcutaneous zone): The most superficial zone, located between the skin and anterior fascia.

  • Lesions in this zone are typically not breast-related (e.g., lipomas or cysts).

• Mammary zone: The middle zone, situated between the anterior and posterior mammary fascias.

  • Contains lobar ducts, duct branches, TDLUs, and the majority of fibrous stromal elements.
  • This zone accounts for most true breast pathology.

• Retro-mammary zone: The deepest zone, located behind the posterior mammary fascia and in front of the pectoral muscle.

  • Contains fat, blood vessels, and lymphatics.

Areola/Nipple Complex

• The nipple is a raised area on the anterior surface, consisting of closely spaced duct openings (lactiferous ducts).
• The areola is a pigmented circular area surrounding the nipple and contains sebaceous glands.

Cooper's Ligaments

• Suspensory ligaments, continuous with mammary fascia, run between lobules and support the breast from deep muscle to skin.

Blood Supply and Drainage

• Arterial supply: Internal thoracic (mammary) artery, lateral thoracic artery, and intercostal arteries.
• Venous drainage: Superficial and deep veins.

Lymphatic Drainage

• Most drainage is towards axillary lymph nodes.
• Sentinel lymph nodes are the first site of nodal metastases and often removed with breast lesions.
• Intra-mammary nodes may exist within the breast, sometimes mistaken for breast pathology.

Breast Physiology

• Breast growth and development are fueled by estrogen and progesterone.
• Milk production is controlled by anterior pituitary and hypothalamus glands.
• Hypothalamus produces prolactin-inhibiting factor (during non-production phase).
• Anterior pituitary produces prolactin (for milk production during and after childbirth).
• Additional hormone oxytocin stimulates milk secretion (lactation). Lactation is also stimulated by infant suckling, which contracts lactiferous ducts.
• After menopause, reduced hormones cause breast tissue atrophy.

Breast Sonography

• Ultrasound (US) is not a primary breast screening tool.
• US has lower sensitivity compared to mammography, making microcalcification detection problematic.
• US may present pseudo-lesions and its interpretation is highly operator-dependent.
• US should supplement mammography (e.g., after mammogram)

Indications for Breast Ultrasound

• Identify and evaluate masses seen in mammograms.
• Differentiate between cysts and solid masses.
• Asses palpable masses.
• Diagnose patients with radiation contraindications (e.g., pregnant/lactating women).
• Analyze infected breast abscesses.
• Investigate nipple discharge.
• Examine issues from breast implants.
• Guide biopsy and other interventional procedures.

Breast Ultrasound Examination Details

• Patient position: Varies by quadrant (inner/outer) and may require supine/oblique/ipsilateral arm positioning, and occasionally upright.
• Equipment: Requires 7-15 MHz linear transducers (frequently including a stand-off pad) with gel application. Image optimization using techniques like split-screen imaging, document compression, mobility, and color assessment (including power/harmonic), and Extended FOV.

Breast Ultrasound Annotation

• Annotation must include: breast laterality, scan plane (various), quadrant, clock position, distance from the nipple, breast body markers.

Scan Planes

• LG and TR: Standard planes.
• RAD: Radial plane, useful for evaluating ducts (oriented radially from nipple).
• ANTIRAD: Anti-radial plane, perpendicular to RAD.

Quadrant Method

• Divides the breast into four quadrants (UOQ, UIQ, LOQ, LIQ).

O'Clock Method

• Each breast region is assigned to a clock face position.

Distance from the Nipple

• Distance to the nipple is measured for lesion location in centimeters.
• Some facilities use additional zones (e.g., subareolar and axillary)

Special Breast Techniques

• Compression can vary to evaluate lesion compressibility and internal mobility (including ballottement).
• Heel-toeing technique is used for perpendicular incidence on Cooper's ligaments for better visualization.
• Positional changes facilitate visualization of different quadrants.
• Peripheral compression is helpful for evaluating under nipple/areola areas.
• Rolled nipple technique is used on patients with nipple discharge while the nipple is rolled under the probe.
• Two-handed technique helps with compressing the nipple/areola region between the hand and the transducer.

Other Sonographic Techniques

• Elastography: Uses lesion stiffness to assess malignancy likelihood (color-coded images), via operator compression.
• Shear wave elastography: Uses transducer force for quantitative assessment of stiffness.
• 3D: Hand-held or Automated Breast Ultrasound System (ABUS).
• CEUS: Contrast-enhanced ultrasound; further research is needed.

Sonographic Appearance (Breast)

• Depends on factors such as age and functional state of the woman.
• Visually appears in 3 layers (pre-mammary, mammary, and retromammary); (not always distinguishable).
• Pre-mammary layer demonstrates skin complex (hypoechoic band between two hyperechoic lines, <2 mm thick).
• The nipple/areolar complex may create shadows when scanning directly over the nipple.
• Fatty lobules are hypoechoic and elongate upon compression.
• The mammary layer presents homogeneous glandular tissues (medium to hyperechoic echoes).
• Ducts and ductules are anechoic, hypoechoic, or isoechoic, and tubular or round.
• Cooper's ligaments are echogenic and linear.
• Retromammary layer features fat lobules, blood vessels, lymphatics, and hypoechoic pectoral muscle. Ribs appear as curved echogenic structures with shadowing .
• Age-related changes impact appearance (younger: more parenchymal tissue, denser, echogenic; older: more fatty tissue, more hypoechoic).

Correlating US to Mammogram

• Ensure mammographic and ultrasound findings pertain to the same lesion.
• Sonographers should understand basic mammographic principles for accurate correlation.

Mammography (Basics)

• Radiographic procedure for breast examination.
• Uses ionizing radiation.
• Gold standard for breast screening, utilizing compression paddle.
• Multiple positions/views are captured for comprehensive evaluation.

Mammography (Standard Views)

• Cranio-caudal (CC): X-ray directed from head to feet, determining medial/lateral lesion location.
• Medio-lateral oblique (MLO): X-ray directed from medial to lateral, determining superior/inferior lesion location.

Mammography-US Correlation (Basic Lesion Location)

• Correlate lesion location in mammogram with ultrasound identification.
• Indicate superior/inferior/medial/lateral position in both modalities.

Mammography (Alternate Views)

• 90° Lateral: Perpendicular to craniocaudal view.
• Spot compression: Focal compression on suspected lesions for detailed evaluation.

BI-RADS Nomenclature

• American College of Radiology developed system.
• Standardized breast lesion reporting.
• Guides management decisions based on defined categories (0-6).

Breast Interventions

• Offers methods for addressing breast lesions (e.g., biopsies, cyst aspiration, needle localization).
• Biopsies: Large-needle biopsies target solid lesions, while thin-needle biopsies target cysts.
• Localization: Used prior to surgery; places a marker in the lesion for precise removal.