Mammography or breast ultrasound

Complementary modalities

Complementary, not alternative - the choice is driven by age and breast density, and by whether the question is screening or diagnostic

Modality	Best for	Weakness
Mammography	Microcalcification (DCIS), screening >=40-50, fatty breasts	Dense breasts - lesion and parenchyma are both white
Ultrasound	Young/dense breasts, cyst vs solid, axilla, image-guided biopsy	Not a screening test; operator-dependent; poor for calcification
MRI	Highest sensitivity; extent of disease, lobular cancer, high-risk screening, occult primary, implant integrity	Low specificity -> false positives and additional biopsies

Contrast-enhanced mammography is emerging as an MRI alternative where access is limited

BreastScreen Australia: free biennial screening mammography, actively invites 50-74; available on request 40-49 and 75+
Mammographic sensitivity ~85% overall, but falls to ~50-70% in extremely dense breasts
~40% of women aged 40-74 have dense breasts; density falls with age and rises with HRT
Dense breast tissue is both a masking factor AND an independent risk factor for breast cancer - a favourite exam point

Mammographic contrast depends on differential X-ray attenuation between fat (radiolucent) and fibroglandular tissue/tumour (radiodense)
- Dense parenchyma and cancer have the same density -> masking
Ultrasound distinguishes by acoustic impedance - cysts are anechoic with posterior enhancement; cancers are hypoechoic, taller-than-wide, with irregular margins and posterior shadowing
MRI depends on neovascularity and contrast kinetics - rapid enhancement with washout

Clinical + imaging + pathology. All three; a discordant result mandates further investigation regardless of how reassuring the other two are.

<35 years -> ultrasound first (dense breast, low cancer probability, radiation avoidance); add mammography if imaging or clinical findings are suspicious
>=35-40 -> mammography + targeted ultrasound
Pregnancy/lactation -> ultrasound first; mammography is safe with shielding if needed

Spiculated mass, architectural distortion
Pleomorphic, branching, linear or clustered microcalcification - the hallmark of DCIS
Asymmetric density, skin or nipple retraction
Two views: craniocaudal and mediolateral oblique; tomosynthesis (3D) improves detection in dense breasts and reduces recall

*Mammography characteristically UNDERESTIMATES the extent of invasive lobular carcinoma*
- Grows diffusely and infiltratively in single-file cords without forming a discrete mass
- E-cadherin negative -> loss of cell cohesion -> no mass effect
- -> MRI is required for accurate size assessment and to exclude multifocal/contralateral disease before planning breast-conserving surgery
Also frequently occult: DCIS without calcification, disease behind implants, very posterior lesions

BI-RADS 0 incomplete; 1 normal; 2 benign; 3 probably benign (<2% malignancy, 6-month follow-up); 4 suspicious (biopsy); 5 highly suggestive (>95%); 6 biopsy-proven

Average risk: BreastScreen biennial mammography 50-74
Moderately increased risk (family history): annual mammography, often from 40
High risk - BRCA1/2, TP53, prior chest radiotherapy before 30, >30% lifetime risk:
- Annual breast MRI from age 25-30, plus mammography from 30-40
- dec stage 2+ diagnoses ~70%; proven mortality benefit only in the Hodgkin-radiotherapy cohort
- MRI is Medicare-rebated in Australia for women under 50 at high risk

Core biopsy, not FNA - core gives histology, grade, invasion and receptor status
- FNA retains a role for axillary node sampling and simple cyst aspiration
Image-guided (US preferred; stereotactic for calcification-only lesions; MRI-guided if only MRI-visible)
Clip placement at biopsy if neoadjuvant therapy is planned - the tumour may become undetectable
Discordant triple assessment -> excision biopsy

*A normal mammogram does not exclude cancer in a woman with a palpable lump* - proceed to ultrasound and biopsy
Do not use screening mammography to investigate a symptomatic patient - refer for diagnostic assessment
Breast pain alone is rarely cancer, but a lump, nipple discharge (bloody or single-duct), or skin change is

Dense breast tissue - risk factor and masking factor; density notification is being progressively introduced in Australian screening programmes
Invasive lobular carcinoma, DCIS, Paget's disease of the nipple
Prior chest radiotherapy for Hodgkin lymphoma - MRI surveillance indication
BRCA1/2, TP53, PALB2 - high-risk MRI surveillance
Breast implants - MRI for rupture; implant-associated anaplastic large cell lymphoma
HRT - increases density and reduces mammographic sensitivity
Male breast cancer - mammography and ultrasound both used

Screening mammography reduces breast cancer mortality by ~20-25% in the invited population
Harms: false positives (~10% recall rate, most resolved by further imaging), overdiagnosis of indolent DCIS (estimated 10-20% of screen-detected cancers), radiation exposure (negligible), anxiety
Interval cancers - diagnosed between screening rounds; more common in dense breasts and more often high-grade/triple-negative
Supplemental ultrasound or MRI in dense breasts increases cancer detection but also false positives; not currently part of the Australian screening programme
The screening debate is about the balance of overdiagnosis against mortality benefit - be able to state both sides

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