Breast imaging

Mammogram

• • Situations where it is difficult to get images/interpret
    • <4cm breast tissue when compressed
    • Usually possible to get some images in a man, although not always, and not always useful
    • Sensitivity limited by breast density. Difficult to read in women <30yo. Useful only with high suspicion of malignancy in 30-40yo (start off with mammogram, then try MRI if too dense). Higher fat content is helpful for reading mammograms.
      • 95% sensitivity >60yo
      • 50% sensitivity <40yo
    • BIRADS classification for breast density:

• • • Technique
      • Breast compression
        • Reduce the thickness of the tissue through which the radiation must pass
        • Separate adjacent structures
        • Improve resolution
      • Views
        • Typically mediolateral oblique (MLO) and craniocaudal (CC)
          • MLO needs to have visible pectoralis major
          • Note that the two views are not at right angles to one another
        • Magnification views to evaluate calcifications
        • Compression views to provide additional detail for mass lesions

• • Suspicious findings:
    • Spiculated mass - 81% PPV

• • • Non-calcified mass density (70% malignant if highly dense)
    • Grouped microcalcifications - likely intraductal calcifications in areas of necrotic tumours

• • • Fine pleomorphic or linear branching microcalcifications - especially DCIS

• • Low-energy x-ray: safe during pregnancy
  • 10-15% of clinically evident breast cancers have a normal mammogram.
  • Screening mammography
    • Appears to be most effective for 60-70 year olds
  • Interpretation

Assessment	Management	Likelihood of cancer
Category 0: Incomplete – Need additional imaging evaluation and/or prior mammograms for comparison	Recall for additional imaging and/or comparison with prior examination(s)	N/A
Category 1: Negative	Routine mammography screening	Essentially 0% likelihood of malignancy
Category 2: Benign	Routine mammography screening	Essentially 0% likelihood of malignancy
Category 3: Probably benign	Short-interval (6-month) follow-up or continued surveillance mammography	>0 but ≤2% likelihood of malignancy
Category 4: Suspicious	Tissue diagnosis*	>2 but <95% likelihood of malignancy
Category 4A: Low suspicion for malignancy		>2 to ≤10% likelihood of malignancy
Category 4B: Moderate suspicion for malignancy		>10 to ≤50% likelihood of malignancy
Category 4C: High suspicion for malignancy		>50 to <95% likelihood of malignancy
Category 5: Highly suggestive of malignancy	Tissue diagnosis*	≥95% likelihood of malignancy
Category 6: Known biopsy-proven malignancy	Surgical excision when clinically appropriate	N/A

• • BIRADS 3 should not be used in screening - needs further investigation, so technically a 0

• • Mammogram classification - to allow detection of concordance within the triple test
    • M1: normal
    • M2: benign
    • M3: uncertain but probably benign
    • M4: suspicious and possibly cancer
    • M5: cancer
  • Screening vs diagnostic mammography
    • Screening is just CC and MLO
    • Diagnostic would be where the radiologist is available and specific views are obtained to achieve better resolution on abnormalities, including magnification, compression, lateral
    • Tomography

3D mammography (tomosynthesis)

• • Tomographic images reconstructed from multiple low-dose projection images - like a basic CT
  • Overall dose of radiation is comparable to regular mammogram
  • Gives 1mm slices
  • Good at delineating small and multiple masses, microcalcifications, and distortion due to ducts and vessels
  • Reduces false-positives and cancer detection

Contrast-enhanced mammogram

• • Injection of iodinated contrast agent two minutes prior to mammogram
  • Superior accuracy to mammogram, nearing accuracy of MRI
  • Expect vascular lesions such as malignancy to have contrast uptake

Ultrasound

• • Most useful in determining whether a lesion is solid or cystic, and for discriminating lesions in patients with dense breasts
  • Not a good screening tool - has to be done for a targeted lesion
  • Indications
    • Lump in pregnant/lactating women
    • Lump in patient <30yo (first-line)
    • Lump in patient >30yo (based on clinical suspicion)
    • Mammographic mass
    • Axillary assessment in patients breast cancer
    • Suspicious MMG without mass
  • Findings
    • Shape - ovoid vs irregular
    • Orientation to skin (taller or wider)
    • Internal echotexture
    • Margin - circumscribed vs non-circumscribed
    • Vascularity
    • Posterior acoustic features - enhancement/variable/shadowing
  • Suspicious features
    • Hypoechoic
    • Solid mass
    • Irregular border
    • Taller than wide, invading through tissue planes
    • Posterior acoustic shadowing
    • Internal vascularity
    • Lobulated
    • Associated abnormal lymph nodes in axilla

• • • • Short axis >3mm
      • Loss of fatty hilum
      • Asymmetrical cortical thickening
      • Calcifications
      • Round instead of oval
      • Hypervascular

• • Reassuring features
    • Circular appearance (especially in younger women)
    • Containing fat, which is uncommon in breast cancers
  • Classification
    • U1: normal
    • U2: benign
    • U3: uncertain but probably benign
    • U4: suspicious and possibly cancer
    • U5: cancer

MRI

• • Technique
    • Generally done with gadolinium contrast - detect neovascularisation
    • Elective MRI should be performed between menstruation and ovulation to account for variation in blood flow and epithelial proliferation
    • The contrast is not safe in pregnancy
  • Indications
    • Identifying primary lesions

• • • • Identify the primary tumour in the breast for patients that present with unknown primary axillary metastases
      • Identify the primary tumour in Paget's disease of the nipple
      • Assessing size/extent of primary tumour, especially in younger women with dense breast tissue
      • Evaluating for the presence of multifocal or multicentric cancer
      • Evaluating invasive lobular cancer where BCS is planned

• • • Assessing treatment response

• • • • Identify extent of residual disease after lumpectomy with positive margins
      • Assess treatment response after neoadjuvant chemotherapy

• • • After implants

• • • • Assess implant rupture
      • Assess breast when silicone injections have been used

• • • Screening

• • • • Can be done annually in women with high risk

• • Sensitivity approaching 100% for invasive cancer, and up to 92% for DCIS
  • Specificity not as good as mammogram or USS - high false-positive rate
  • Always do mammogram at the same time - MRI may miss some malignancies that a mammogram would detect
  • Generally not recommended for women with a lifetime risk of breast cancer <15% (higher risk of false positive)
  • Need to wait 19 months after surgery to differentiate cancer and scar
  • Can demonstrate axillary disease, but sensitivity not adequate to replace SLNB
  • Good for assessing spinal metastases

CT

• • Not currently done for any indications