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Anatomy and Normal Variants

Segmental Anatomy

Segmental Anatomy

Wendie A. Berg, MD, PhD, FACR, FSBI

TERMINOLOGY

Definitions
- Lobe (segment): Drainage territory defined by each major duct
  - Typically 12-16 or more lobes in each breast, each terminating in nipple orifice
- Segmental distribution: Expected territory of duct and its branches with apex directed toward nipple
  - Can be seen as Ca⁺⁺, masses, or asymmetry on mammography, US
  - Mass or nonmass enhancement on MR
- Terminal duct: Final branch of segmental duct
  - 2 parts: Extralobular terminal duct (ELTD) and intralobular terminal duct (ILTD)
- Lobule: Composed of ILTD and complex system of tiny ducts terminating in blind-ending acini (alveoli)
- Terminal duct lobular unit (TDLU): Lobule + ELTD

IMAGING ANATOMY

Lobe/Segment
Ductal System
Terminal Duct Lobular Unit

CLINICAL IMPLICATIONS

Clinical Importance

ANATOMY IMAGING ISSUES

Mammography
Ultrasound
MR

Related Anatomy

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Related Differential Diagnoses

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References

Tables

Tables

TERMINOLOGY

Definitions
- Lobe (segment): Drainage territory defined by each major duct
  - Typically 12-16 or more lobes in each breast, each terminating in nipple orifice
- Segmental distribution: Expected territory of duct and its branches with apex directed toward nipple
  - Can be seen as Ca⁺⁺, masses, or asymmetry on mammography, US
  - Mass or nonmass enhancement on MR
- Terminal duct: Final branch of segmental duct
  - 2 parts: Extralobular terminal duct (ELTD) and intralobular terminal duct (ILTD)
- Lobule: Composed of ILTD and complex system of tiny ducts terminating in blind-ending acini (alveoli)
- Terminal duct lobular unit (TDLU): Lobule + ELTD

IMAGING ANATOMY

Lobe/Segment
Ductal System
Terminal Duct Lobular Unit

CLINICAL IMPLICATIONS

Clinical Importance

ANATOMY IMAGING ISSUES

Mammography
Ultrasound
MR