01Core principlesThe concepts and mechanisms needed to understand the subject.
Breast imaging is selected by the anatomical question and by age or physiological context. Ultrasound is first-line for women under 40 and during pregnancy or lactation; mammography is first-line from 40, with ultrasound added when indicated. Suspicious clinical or sonographic findings can require mammography below 40, and confirmed malignancy requires mammographic assessment irrespective of age.
MRI protocols are not interchangeable. Dynamic contrast-enhanced MRI addresses selected oncological questions such as extent, lobular disease or an occult primary, whereas suspected implant rupture starts with ultrasound and uses a dedicated non-enhanced implant MRI only when ultrasound is equivocal. Every report must state whether the clinical target was seen and explained, because negative imaging cannot settle a discordant suspicious finding.
Key points
- Use ultrasound first in women under 40 and during pregnancy or lactation; target the palpable or axillary site and use ultrasound to guide a needle when it displays the lesion.
- Use mammography first from age 40, adding ultrasound as indicated. Perform mammography at any age for confirmed malignancy and for a U4 or U5 lesion, preferably before biopsy; consider it below 40 for P4 or P5 clinical findings.
- Use dynamic contrast-enhanced MRI for defined oncological questions such as selected local staging, lobular extent, mammographically occult cancer or an occult breast primary, rather than as a generic superior test.
- For suspected implant rupture, start with ultrasound. A normal or unequivocal ultrasound usually needs no integrity MRI; equivocal findings call for a dedicated non-enhanced implant-protocol MRI.
- Pregnancy does not justify delaying indicated ultrasound, core biopsy or mammography. Current RCR guidance does not require shielding for mammography and advises against breast MRI during pregnancy because diagnostic sensitivity is reduced.
- An additional enhancing focus is not automatically malignant: correlate it with targeted imaging and obtain tissue when feasible before it changes the planned operation.
02Mechanisms and patternsImportant relationships and how to distinguish them.
Ultrasound distinguishes many cystic from solid lesions, examines a palpable focus and axilla dynamically, and guides sampling without ionising radiation, but operator technique and lesion conspicuity matter.
Mammography surveys both breasts and depicts calcification, distortion and asymmetry; density can obscure lesions, and a negative study does not cancel a strongly suspicious clinical finding.
Dynamic contrast-enhanced MRI maps selected cancer questions but may generate false-positive enhancements. Implant integrity instead uses a dedicated non-enhanced protocol only after equivocal ultrasound.
Ultrasound leads below 40 and in pregnancy or lactation; mammography leads from 40 and remains indicated below 40 when malignancy is confirmed or findings are sufficiently suspicious.
03Interpreting evidenceInformation, measurements and their limitations.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Targeted ultrasound - Why
- Resolve a focal palpable, inflammatory or axillary question and guide intervention.
- Interpretation and limitations
- Correlate the transducer finding with the exact clinical site; a benign incidental lesion elsewhere does not explain a separate palpable abnormality.
- 02
Diagnostic mammography - Why
- Assess calcification, architecture and bilateral distribution with dedicated views.
- Interpretation and limitations
- Compression and additional views may resolve summation; breast density and incomplete coverage limit sensitivity, so the report must answer the stated symptom.
- 03
Question-specific breast MRI - Why
- Use contrast-enhanced MRI for selected oncological staging or occult-primary questions, or non-enhanced implant MRI after equivocal ultrasound.
- Interpretation and limitations
- Protocol and indication must be stated. Enhancement is not cancer-specific and may require targeted biopsy; implant-integrity sequences answer rupture rather than tumour vascularity.
- 04
Image comparison and categorisation - Why
- Turn morphology and interval change into an actionable assessment.
- Interpretation and limitations
- Compare priors whenever possible, document the assessment category and recommend the modality capable of sampling any residual suspicious target.
04Applied reasoningWorked examples connecting principles to decisions.
01Worked case: integrated breast assessmentApply ultrasound, mammography and breast mri selection to a defined presentationA 34-year-old pregnant patient has a new hard 2 cm breast mass. They are worried that any imaging could harm the fetus and ask to wait until after delivery.+
- 1Define and map the mass clinically, document gestation and explain that pregnancy changes test selection but does not justify delaying diagnosis of a suspicious lesion.
- 2Request targeted breast and axillary ultrasound first, using it to characterise the palpable target and provide a route for image-guided core biopsy.
- 3If ultrasound is U4 or U5, complete mammography preferably before biopsy; perform mammography irrespective of age once malignancy is confirmed, without presenting abdominal shielding as routinely necessary.
- 4Avoid substituting breast MRI for tissue diagnosis during pregnancy. Current RCR guidance advises against pregnancy MRI because background enhancement reduces sensitivity; seek specialist radiology input only for an exceptional unresolved question.
- 5Verify that imaging and core sampled the same coordinates, and ensure the result reaches both breast and obstetric teams with a named next appointment.
02Modality selectionMatch the test to the unresolved questionA clinician must choose imaging for a symptomatic breast abnormality with no previous assessment.+
- 1Define whether the question concerns a palpable mass, calcification, discharge, implant, axillary node or known-cancer extent; one generic breast scan cannot answer every problem.
- 2Start with ultrasound under 40 or during pregnancy and lactation, and mammography from 40. Add mammography below 40 for confirmed malignancy, U4/U5 imaging or selected P4/P5 clinical findings.
- 3For implant symptoms, use ultrasound first and request dedicated non-enhanced implant MRI only if rupture findings remain equivocal; use contrast-enhanced MRI only for an oncological indication.
- 4Mark the symptomatic coordinates, state the remaining limitation and arrange tissue diagnosis when suspicious clinical or radiological findings remain.
03MRI finding pathwayVerify an additional enhancing focusStaging MRI detects a separate enhancement that would convert planned breast-conserving surgery to mastectomy.+
- 1Review the MRI morphology and location with the original mammography and ultrasound to confirm that the focus is genuinely separate and management relevant.
- 2Perform second-look targeted ultrasound or mammographic review to find a simpler biopsy route while keeping exact MRI coordinates.
- 3Obtain image-guided tissue when feasible before expanding surgery, because enhancement has benign as well as malignant causes.
- 4Revisit operative options in the multidisciplinary team after pathology, documenting whether the extra focus changes extent, localisation or patient choice.
05Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.
- For a palpable lesion, record whether ultrasound and mammography visualised the exact site and what limitation remains if either study is negative.
- After MRI, track every additional management-relevant focus to a documented correlate, biopsy or explicit multidisciplinary decision not to sample.
- When short-interval imaging is chosen, specify the lesion, modality and comparison date so stability is assessed on the same feature.
- Before oncological contrast-enhanced MRI, check renal, contrast, device and pregnancy information required by local safety processes; label implant-integrity requests explicitly as non-enhanced protocol studies.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Sensitivity does not equal certainty
MRI may reveal more enhancements than mammography, yet benign tissue also enhances. High sensitivity can increase additional tests, so a management-changing focus should be verified when feasible.
Calcification belongs to mammography
Ultrasound can occasionally show a correlate, but mammography characterises the distribution and morphology of microcalcification and supplies the route for stereotactic sampling when no sonographic target exists.
A target must be visible to guide a needle
The appropriate biopsy method follows the modality that demonstrates the lesion. Ultrasound guidance is unsuitable for an abnormality that exists only on mammography or MRI.
Physiology changes appearance
Pregnancy and lactation alter density, vascularity and benign lesion behaviour. Radiology interpretation needs that context, while persistent suspicious findings still require timely diagnosis.
07Common pitfallsFrequent interpretation and management errors.
- 01
Ordering MRI simply because it is perceived as the most sensitive test can generate findings that do not answer the original clinical question.
- 02
Calling a palpable lump normal after negative mammography in dense tissue ignores both modality limits and the need for targeted correlation.
- 03
Biopsying an approximate area under ultrasound when the lesion is visible only on mammography risks a non-representative benign result.
- 04
Changing the planned operation for an unverified MRI focus can expose the patient to avoidable surgery for a false-positive finding.