Normal breast US appearance
- Tissue
- Premammary zone (hypoechoic)
- Mammary zone (hyperechoic)
- Retromammary zone (hypoechoic)
- Pectoralis major (hyperechoic)
- Cooper’s ligament (hyperechoic bands)
- Course oblique through subcutaneous fat
- Ducts
- Collapsed (central bright echo)
- Mildly ectatic (2 hyperechoic lines, anechoic lumen)
- Severely ectatic (2 further separated hyperechoic lines)
- TDLUs
- ~2mm hypoechoic structures
- Larger with adenosis + pregnancy
Breast tissue layers
- Premammary
- Superficial: skin → ant mammary fascia
- Skin (epidermis + dermis), subcutaneous fat, coopers ligaments
- Lesions: usually not true breast lesions (e.g. lipoma, subcutaneous cyst) - Mammary
- Middle: ant mammary fascia → post mammary fascia
- Lobes, ducts, interlobular stroma
- Where most breast lesions arise - Retromammary
- Deep: post mammary fascia → chest wall
- Fatty tissue, coopers ligaments
- Best seen with mamms (US = not well seen - compression against chest wall)
Breast function
Modified sweat gland
- Secretes milk
- Lobules drain → lactiferous ducts → nipple
Hormones that affect breast development + function:
- Estrogen (promotes lobule enlargement + duct development)
- Progesterone (increases number/ size of lobules for breastfeeding)
- Prolactin (promotes milk production + excretion)
Breast anatomy
- 15-20 lobes
- 20-40 lobules per lobe
- Lobules
- ‘Terminal ductal lobular unit’ (TDLU)
- Functional unit
- Concentrated in upper outer quad (site of most pathology)
Contains:
- Alveoli (produce milk)
- Intralobular terminal duct (central space of lobule)
- Intralobular stroma (loose CT around alveoli)
- Extralobular terminal duct (attached lobule → ductal system)
- Interlobular stroma
- Dense CT (surrounds TDLU)
- Lactiferous ducts
- Drain milk from ETD → nipple
- Stroma
- Space between lobes
- Adipose (most of breast volume)
- Fibrous connective tissue (coopers ligaments)
Breast lymphatic drainage
- Axillary nodes (75%)
- Lat lobes → subareolar lymphatic plexus (superficial) → axillary nodes → subclavian lymphatic trunk → venous system
- Levels = determined by location relative to pec minor m. (1→2→3)
- Level 1: inf to pec minor
- Level 2: post to pec minor
- Level 3: sup to pec minor - Parasternal nodes
- Med lobes → parasternal nodes → bronchomediastinal lymphatic trunk → venous system
- Lie in chain lat to sternum - Intramammary nodes
* *-** Within breast
- BC typically metastasizes via lymphatics
- Sentinel node: first node involved by mets (usually level 1 axillary)
Breast cancer: DCIS vs invasive ductal carcinoma
Brest cancer = luminal epithelial ells proliferate
- DCIS: confined within duct (no ext beyond basement membrane)
- Invasive ductal ca: extends beyond duct (basement membrane)
Gynecomastia
Benign hypertrophy of ductal elements in male breast tissue
Causes:
- Puberty
- Disease process
- Medications
Presents:
- Enlarging breast
- Soft palpable mass
Hypoechoic mass
Male breast cancer
Rare
Risk factors:
- Older age
- BRCA 2 gene
- Family history
- Radiation exposure
- Klinefelter’s syndrome (extra X chromosome e.g. XXY)
- Testicular disease
Presents:
- Hard enlarging mass
Hypoechoic heterogeneous mass
Ruptured silicon implant
- Intracapsular: silicon leaks → confined within fibrous scar tissue
- Extracapsular: silicon leaks → beyond fibrous scar tissue
Presents:
- Pain, burning, tingling, numbness
- Redness
- Distorted breast shape
- Hardening of breast
Discontinuation of membrane
‘Snowstorm’: poorly marginated echogenic area with dirty shadowing
Duct ectasia
Abnormal duct widening >2mm
- Due to benign or malignant process
- Benign: chronic inflammatory + fibrotic changes → thickening of debris → calcification
- Malignant: intraductal malignancy
Presents:
- Post menopausal + smokers
- Asymptomatic
- Nipple discharge + retraction
- Pain
- Palpable mass
- *Branching tubular structures >2mm**
- Anechoic or echogenic (inspissated secretions) contents
Acute mastitis
Inflammation of breast tissue
- Puerperal
- 6 weeks post-birth (lactating women)
- Common
- Causes: infection, milk stasis
- Risk factors: primiparous (1st birth), cracked/damaged nipple, smoking, diabetes
- Non-puerperal
- Non-lactating
- Cause: underlying mass
Presents:
- Pain, swelling, redness
- Nipple discharge + retraction
- Enlarged lymph nodes
- Elevated inflammatory markers
Treatment:
- Antibiotics
- Aspiration/ surgical drainage
- *Heterogeneous ill-defined region**
- Echogenic inflammatory fat
- Hypoechoic glandular parenchyma
- Dilated ducts
Hypervascular
Skin thickening
Reactive axillary lymph node
- *Retroareolar abscess** (complicated)
- Hypoechoic heterogeneous fluid collection
- Mobile debris
- Irregular margins
- Posterior enhancement
- Hypervascular walls (avascular within)
- Differentials:*
- Inflammatory breast cancer*
- Hematoma*
Benign breast nodule findings
- Totally hyperechoic (normal interlobular stroma)
- Elliptical/ oval/ gently lobulated (3 or less)/ wider than tall
- Thin echogenic capsule
Fibrocystic change
Benign alteration of TDLUs of breast
- Very common (90%)
- Normal physiological process of breast tissue
- Fluctuates with hormone cycles
Presents:
- 20-40yrs
- Pain (worse during ovulation)
- Swelling
- Palpable nodule
- *Multiple small cysts in mammary zone**
- Well circumscribed, thin walls (dilation of ducts)
Increased fibrous stroma
Fibroadenoma
Proliferation of fibrous (fibro) + glandular (adenoma) tissue
- Most common benign tumour
- Hormone-sensitive
- Enlarge during pregnancy/ lactation
- Decrease post menopause
Present:
- Young women (< 30)
- Mobile palpable lump
- Slow growing
- Sudden pain → hemorrhage
Treatment:
- Biopsy if enlarging
Oval or macrolobulated mass
Hypoechoic
Well circumscribed/ smooth margins
Homogeneous
Wider than tall
Posterior enhancement
Can have:
- *- Calcifications**
- *- Internal vascularity**
Lipoma
Mature adipose tissue
- Common
- Benign
Presents:
- Painless palpable lump
- Soft + mobile
- Middle-aged/ menopausal women
Treatment:
- Biopsy if enlarges
- *Round mass**
- Compressible
- *Isoechoic or hyperechoic to fat**
- May contain multiple thin echogenic septations (parallel to skin)
Epidermal inclusion cyst
- Benign
- Dilated + obstructed hair follicle
- *Small hypoechoic lesion in superficial tissue**
- Oblique track to skin surface
Posterior enhancement
- *Avascular**
- Can become infected (peripheral vascularity)
Oil cyst
Injury to breast → area of focal fat necrosis
- Common
Causes:
- Surgery
- Trauma
- Radiation
Presents:
- Older women
- Non-tender/ tender palpable lump
- *Complex cyst**
- Low-level echoes
- Fluid-debris level
- Irregular wall
- Thick septations
- Mural nodules
- Calcification (+/- shadowing)
Avascular
Differential = hematoma
Intraductal papilloma
Benign tumour in walls of milk ducts
- Leads → duct obstruction
- May contain atypical cells/ areas of cancer
- Central intraductal
- *-** Most common
- Large duct
- If expands duct → risk of malig
- Peripheral intraductal
- *-** Grow in TDLUs
- Higher risk of malig.
Presents:
- Post menopause (40-50yrs)
- Asymptomatic
- Nipple discharge (bloody or clear)
Central intraductal:
- Intracystic lesion with vascular stalk
- Solid mass filling duct
Large duct:
- Solid isoechoic mass in dilated duct with vascular stalk
Peripheral:
- Solid lesion involving TDLUs +multiple peripheral ducts
Differential = early DCIS
Intramammary lymph node
Lymph node within breast tissue
- Can be benign or malignant
- Common
- Usually upper outer quad
Solitary/ multiple nodes
Benign features: oval, hypoechoic to breast tissue, echogenic vascular hilum
Malignant features: round, very hypoechoic, homogeneous, >1cm
Galactocele
Cyst containing milk (‘lactocele’)
- Occurs due to lactiferous duct occlusion
Presents:
- Lactating women
- Painless soft lump
Treatment:
- Most resolve spontaneously
- US-guided aspiration
- *Complex cyst**
- Internal debris
- Fat-fluid level
Avascular
- Differentials:*
- Abscess*
- Fibroadenoma*
- Breast ca*
Ductal carcinoma in situ (DCIS)
- Adeno carcinoma confined to ducts
- Proliferation of abnormal epithelial cells
- No extension beyond basement membrane (cannot metastasize)
Presents:
- Asymptomatic (most)
- Nipple discharge
- Palpable lump
Risk factors:
- Increasing age
- Family hx
- Nulliparity
- Age 30+ at birth of 1st child
Treatment:
- Lumpectomy (small)
- Mastectomy (large/ 2+ tumors)
- Radiation
- Hormonal therapy (tamoxifen)
Clinical signs of breast cancer
- Growing lump
- Hard
- Does not fluctuate with cycle
- Nipple discharge, retraction, non healing ulcer
- Skin dimpling
- Hot, red breast
Ductal carcinoma in situ (DCIS)
- Adenocarcinoma confined to ducts
- Proliferation of abnormal epithelial cells
- No extension beyond basement membrane (cannot metastasize)
- Prognosis = treatment → good, untreated → IDC
Presents:
- Asymptomatic (most)
- Nipple discharge
- Palpable lump
Risk factors:
- Increasing age
- Family hx
- Nulliparity
- Age 30+ at birth of 1st child
Treatment:
- Lumpectomy (small)
- Mastectomy (large/ 2+ tumors)
- Radiation
- Hormonal therapy (tamoxifen)
Hypoechoic intraductal mass
Microlobulations (1-2mm)
Calcificaitons
Invasive ductal carcinoma
Adenocarcinoma extending beyond ducts (basement membrane)
- Most common breast cancer (80%)
- Metastasize via blood + lymph
Grades
- 1 (low) = well-differentiated (less likely to spread)
- 2 (moderate)
- 3 (high) = poorly differentiated (likely to spread)
Present:
- Hard immobile mass
- 50-60yrs
- African Americans
Treatment:
- Lumpectomy
- Mastectomy (partial/ total)
- Radical mastectomy (includes muscle + lymph nodes)
- Chemotherapy
- Radiation
- Hormonal therapy (tamoxifen)
- *Hypoechoic mass**
- Ill-defined
- Hyperechoic angular margins
- Spiculations or thick halo
- Ductal extension
- Branched pattern
- Microcalcifications
- Vascular
Non-compressible
- *Acoustic transmission**
- *-** Post shadowing (grade 1)
- Post enhancement (grade 3)
