Sunday, March 12, 2017

Screening Mammography

This post is derived from notes I took during training. Any images are copyright their respective owners.

  • Screening mammogram (MG) is monthly self breast exam between ages 20-39, annually after 40
  • High risk women should begin screening 10 yrs before the age of diagnosis in their relative
  • Goal PPV > 25%, recall rate ≤ 10%.
  • Offline reading (interpretation after patient has left the department) reduces recall rate.
    • Requires assigning BI-RADS in each mammo report
    • ONLY applies to mammography (not US, MRI)
    • Does NOT require reporting density
    • Each patient must receive their mammography report within 30 days; letter is in lay terms
  • Breast density: predominantly fatty, scattered fibroglandular, heterogeneously dense, extremely dense
    • Patients with 75% dense breasts have five-fold risk elevation
  • Views
    • Cranio-caudal (CC)
    • Mediolateral oblique (MLO)
      • Angle 40 to 60° with breast aligned with arm, pectoralis muscle seen to post nipple line, nipple in profile
    • If lesion is seen on only one view, consider mediolateral (ML) or exaggerated views.
    • Mediolateral (ML)
      • A popular mnemonic for remembering how findings on the lateral view relate to the MLO view is "lead sinks" (lateral lesions appear lower) and "muffins rise" (medial lesions appear higher).
    • Axillary tail view (Cleopatra, XCCL): includes only lateral breast/axilla
    • Tangential view: eval skin lesions
    • Cleavage view: eval lesion in medial posterior breast close to sternum
    • Rolled CC view: eval lesion seen only on CC. Roll upper breast lateral or medial and see how lesion moves
    • Implant displacement (Eklund) view
  • A screening mammogram consists of only CC and MLO views (with possible exaggerated or implant displacement views if indicated or at the technologist's discretion)
  • Palpable masses are always diagnostic mammos, must always get f/u imaging (US)
  • If patient presents with new concern within 6 months of last MG, the MLO and CC views are not repeated, but ML and spot compression views of the palpable concern with a skin marker are appropriate
  • Lexicon - set of terms used to describe mass or focal asymmetry
  • Margins - COSMIc
    • Circumscribed - benign
    • Obscured - likely benign<75 margin="" seen="" span="">
    • Spiculated - malignant until proven otherwise
    • Microlobulated - serrated edge
    • Indistinct - suspicious for malignancy
  • Density - radiolucent, low, isodense, high (worrisome)
  • Shape - ROLI: round, oval, lobular (only MG), irregular (most suspicious)
  • Calcifications
    • Morphology
      • Skin: use BB / tangential views to identify. The breast is compressed with an open grid paddle in the region of the calcifications. A mammogram is obtained followed by placement of a BB over the calcifications using the grid to localize the X and Y coordinates. An additional mammogram with BB in place is obtained to confirm the BB overlies the calcifications. The breast is then released from compression and positioned such that the BB is tangential to the x-ray source with application of compression followed by magnification mammogram.
      • Tram-track: vascular
      • Popcorn: start peripherally in an involuting fibroadenoma
      • Rod-like: caused by secretory disease (plasma cell mastitis), postmenopausal
      • Round with fluid level: Milk of calcium - Ca++ free in cysts, level on lateral view
      • Dystrophic
      • Egg-shell: peripheral to fat necrosis or cyst
      • Coarse heterogeneous: indeterminate → sterotactic biopsy
      • Fine pleomorphic: vary in size, “dot-dash” appearance → possible biopsy.
      • Fine linear/branching: suspicious for DCIS → biopsy
    • Distribution
      • Diffuse/scattered: benign
      • Regional: > 2 cm, not within duct → benign
      • Linear: suspicious (unless tram track)
      • Grouped/clustered: ≥ 5 ca++ in < 1 cc tissue → suspicious
      • Segmental: > 2 cm, ductal → suspicious
  • BIRADS (Breast Imaging Reporting and Data System)
    • 0: Incomplete Assessment - Follow-up Imaging Required (mammo or US)
    • 1: Negative
    • 2: Benign findings only
      • Ca++ FA, Secretory ca++, oil cysts
    • 3: <2 malignancy="" of="" risk="" span="" usu="">diagnostic unilateral 6, bilateral 12, and bilateral 24 mo f/u)
    • 4: 2 to 95% risk of malignancy
      • E.g. Intracystic mass
    • 5: >95% risk of malignancy
      • E.g. Spiculated mass, fine linear ca++
    • 6: Proven cancer
    • Screening MG are only 0, 1, or 2
  • Ultrasound
    • Margins: circumscribed, angular (only US), spiculated, micro-lobulated, indistinct
    • Shape: round, oval, irregular
    • Orientation: parallel (wider than tall); anti-parallel (taller than wide)
    • A finding’s echogenicity is determined by comparing it with subcutaneous fat.
    • Use US first in women < 40, but if see something suspicious, get MG next.

Table 1: BIRADS Scores, Findings, and Associated Diagnoses


BIRADS
MG
US
Dx
2
Coarse / Popcorn ca++

Ca++ Fibroadenoma
2
Large, Rod-like ca++

Plasma cell mastitis
2
Round lucency

Oil Cyst / fat necrosis
2
Lucent centered ca++

Skin ca++
2
Tram track ca++

Vascular ca++
2
Scattered round/punctate ca++

DDx: FCC, adenosis, skin
2
Rim/Eggshell ca++

Fat necrosis, cyst
2
Dystrophic “lava shaped” ca++

Trauma, surgery
2
‘Breast within breast’ appearance

Hamartoma




3
Isolated, cluster of round ca++

FCC, FA, DCIS
3
Focal asymmetry less dense on spot view

Overlapping tissue
3
Non-palpable, circumscribed mass on baseline mammo

FA, Cyst, IM LN
1.4% malignant
3

Complicated cyst (only low level internal echoes)





4
Amorphous, clustered, unilateral

IDC, DCIS, ADH/ALH, FCC
4
Coarse heterogeneous

DDx: FA, trauma, DCIS
4B
Clustered & pleomorphic

40% DCIS
4

Complex cyst





5
Fine linear, branching “Casting” ca++
Pleomorphic ca++

DCIS
5
Spiculated, irregular, dense mass

IDC


  • Malignancy concern for ca++ distribution
    • Benign: diffuse, regional
    • Intermediate: clustered
    • High: Segmental, linear
  • Breast MRI
    • Evaluate enhancement kinetics from fat sat pre- and post-contrast images
    • Type I (Persistent): continuously ↑ CE, associated with benign lesions 83%
    • Type II (Plateau): rise followed by leveling off, borderline suspicious → BIRADS 4
    • Type III (Washout): rapid uptake and then decrease of contrast. 29-77% chance of malignancy b/c tumors require neoangiogenesis; vessels leak gad into extracellular space → BIRADS 4
    • Morphology more important than kinetic curve (ie Type I irregular mass still needs bx)
    • Enhancement lexicon:
      • A focus of CE is < 5 mm  and is too small to characterize
      • Benign
        • Homogeneous
        • Dark internal septations: very specific for fibroadenoma
      • Suspicious
        • heterogeneous
        • rim CE: high grade IDC, fat necrosis, inflammatory cysts
        • enhancing internal septations
        • central CE
    • Non-mass like enhancement (NMLE)
      • Distribution
        • Benign: diffuse
        • Suspicious: segmental (75% ca), ductal (60%), linear (30%), focal (25% ca), regional (20%), multiple (?)
      • Internal CE
        • Benign: heterogeneous, homogeneous, stippled/punctate (benign)   
        • Suspicious: clumped (51% DCIS =  BR4) , reticular/dendritic (inflammatory ca),
    • Spiculated margin has 80% chance of malignancy → BR 4
    • T2 Fat-Sat ↑ lesions: cysts, FA, LN, fat necrosis, mucinous carcinoma
    • Signal flares occur when skin makes contact with coils→ inhomogeneous fat suppression.
  • MRI High Risk Screening
    • Lifetime breast cancer risk > 20%
    • Untested first degree relatives of BRCA carriers
    • Chest wall radiation b/t 10 and 30 yo
      • Begin MG screening 8 years after radiation but not before age 25, or with MRI
    • Genetic syndromes (Li-Fraumeni, Cowden, Bannayan-Riley-Ravulcaba), or first degree rel
  • If < 40
    • A palpable mass should be imaged by ultrasound +/- biopsy or MG for confirmation (eg fat necrosis)

References: