Anatomy and Mammographic Technique



◊  >90% of nipples contain 5–9 ductal orifices


(b)  multiple other blind-ending orifices: connected to sebaceous glands of 1–4 cm in length


√  bilateral symmetric enhancement pattern of normal nipple:


√  1–2 mm superficial layer of intense linear enhancement


√  underlying region of nonenhancement deep to dermis


Ducts


lactiferous ducts coalesce in subareolar region into 5–8 mm wide lactiferous sinuses exiting in the central portion of nipple; organized into


(a)  central ducts: extending to chest wall


(b)  peripheral ducts: arranged in a radial fashion


Main lactiferous duct → branches dichotomously into segmental duct → subsegmental duct → terminal duct → blunt-ending acinus


Terminal Duct Lobular Unit (TDLU)


(1)  Extralobular terminal duct


Histo:   lined by columnar cells + prominent coat of elastic fibers + outer layer of myoepithelium


(2)  Lobule


(a)  intralobular terminal duct


Histo:   lined by 2 layers of cuboidal cells + outer layer of myoepithelium (for milk propulsion)


Significance:   invasive ductal, papillary, mucinous, medullary adenoid cystic cancers arise from ductal epithelium in TDLU and most commonly appear as spiculated irregular masses ± calcifications / developing asymmetries


(b)  ductules / acini


(c)  intralobular connective tissue


Size:     1–2 (range, 1–8) mm in diameter


Change:


(a)  reproductive age: cyclic proliferation (up to time of ovulation) + cyclic involution (during menstruation)


(b)  post menopause: regression with fatty replacement


Significance:


TDLU is the site of fibroadenoma, epithelial cyst, apocrine metaplasia, adenosis (= proliferation of ductules + lobules), epitheliosis (= proliferation of mammary epithelial cells within preexisting ducts + lobules), ductal + lobular carcinoma in situ, infiltrating ductal + lobular carcinoma


Components of Normal Breast Parenchyma


1.   Nodular densities surrounded by fat


(a)  1–2 mm = normal lobules


(b)  3–9 mm = adenosis


2.   Linear densities


=  ducts and their branches + surrounding elastic tissue


3.   Structureless ground-glass density


=  stroma / fibrosis with concave contours


Parenchymal Breast Pattern (László Tabár)


Effect of breast density on sensitivity:


women in their 40s have a 68% higher risk of a FN screening mammogram compared to older women


Recommendation:   perform mammography during 1st week of menstrual cycle


Inter- and intraobserver variability on breast density:


›  low reliability of interreader density agreement (κ = 0.59)


›  imperfect intrareader agreement (κ = 0.72)


Factors affecting breast density between mammograms:


body mass index, weight changes, age, HRT, dietary intake




missing


Overall odds ratio of breast cancer for > 75% tissue density:


›  compared to 10% density 4.74


›  with interval cancer developed in 1 year 17.81


Relative risk of cancer associated with breast density:


›  breast tissue density of 50–74% 2.92


›  breast tissue density of > 75% 4.64


Pattern I


named QDY = quasi dysplasia (for Wolfe classification)


√  concave contour from Cooper’s ligaments


√  evenly scattered 1–2 mm nodular densities (= normal terminal ductal lobular units)


√  oval-shaped / circular lucent areas (= fatty replacement)


Pattern II


similar to N1 (Wolfe)


√  total fatty replacement


√  NO nodular densities


Pattern III


similar to P1 (Wolfe)


√  normal parenchyma occupying < 25% of breast volume in retroareolar location


Pattern IV = adenosis pattern


similar to P2 (Wolfe)


Cause:    hypertrophy + hyperplasia of acini within lobules


Histo:  small ovoid proliferating cells with rare mitoses


√  scattered 3–7 mm nodular densities (= enlarged terminal ductal lobular units) = adenosis


√  thick linear densities (= periductal elastic tissue proliferation with fibrosis) = fibroadenosis


√  no change with increasing age (genetically determined)


Pattern V


similar to DY (Wolfe)


√  uniformly dense parenchyma with smooth contour (= extensive fibrosis)


Enhancement of Normal Parenchyma on MR


=  Background Parenchymal Enhancement (BPE)


◊  Breast enhancement does NOT correlate with breast density


•  varies among women + within same woman over time


Proper enhancement present if:


›  veins contrasted on MIP


›  both internal mammary arteries depicted


›  nipple enhances


Common pattern of enhancement:


√  bilateral symmetric diffuse enhancement:


√  slow minimal / early enhancement


√  persistent delayed enhancement


√  linear patchy enhancement


√  confluent enhancement on late dynamic scan


Distribution of enhancement:


√  bilateral symmetric enhancement with


(a)  moderate / marked degree of BPE


(b)  diffuse / regional distribution


(c)  homogeneous / internally stippled


√  “picture framing” of vascular inflow = enhancement commonly begins in periphery + gradually becomes apparent in more central breast tissue


√  scattered innumerable 9–10 mm foci of enhancement


√  geographic areas of symmetric regional enhancement


√  multiple larger symmetric areas of enhancement (DDx: asymmetry suggest malignancy)


BPE Effect on Interpretation of MR Images:


1.   Falsely positive ← focal / regional / asymmetric background parenchymal enhancement


2.   Falsely negative ← moderate / marked BPE


Classification of Background Parenchymal Enhancement:
















Minimal    < 25% of glandular tissue
Mild 25–50%
Moderate 50–75%
Marked    > 75%

Hormonal Influence on BPE


1.   Menstruation


√  enhancement high during days 21–28 and days 1–6 after menstruation + low during days 7–20


2.   Lactation


◊  Breast involution after lactation takes 3 months


Note:  NO impairment in cancer detection in lactating patients!


Breast-feeding:   safe after contrast-enhanced MRI ← minute amounts of Gd in breast milk


3.   Postmenopausal period without HRT


√  decrease in fibroglandular tissue → degree of BPE typically less than that in premenopausal women


4.   Hormone replacement therapy (HRT)


√  increase in BPE in amount + degree + distribution with great interindividual variations:


◊  Hormonal effect reverses after 30–60 days


5.   Endocrine antihormonal therapy


Antiestrogenic agents:   selective estrogen receptor modulators, aromatase inhibitors


√  significant decrease in amount of fibroglandular tissue + cysts + BPE


√  effect on BPE evident early in treatment (< 90 days)


√  tamoxifen rebound after medication discontinued:


√  global / focal increase in BPE


6.   Oophorectomy → decrease in BPE



MRI preferably performed during 2nd week of menstrual cycle!

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Jun 29, 2017 | Posted by in GENERAL RADIOLOGY | Comments Off on Anatomy and Mammographic Technique
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