Uterine junctional zone: correlation between histologic findings and MR imaging

Area of Science:

• Anatomic imaging
• Histopathology
• Magnetic Resonance Imaging

Background:

• Uterine zonal anatomy on T2-weighted MRI includes distinct endometrial, junctional, myometrial, and subserosal zones.
• Understanding the histologic basis of these zones is crucial for accurate MR interpretation.

Purpose of the Study:

• To correlate the MR imaging appearance of uterine zonal anatomy with detailed histologic findings.
• To elucidate the microscopic structure responsible for the signal characteristics of uterine zones on MRI.

Main Methods:

• T2-weighted MRI of 17 in vivo and 13 extirpated human uteri.
• Histologic examination using hematoxylin-eosin, Mallory trichrome, and actin immunofluorescence staining.
• Morphometric and electron microscopic analysis of uterine surgical specimens.

Main Results:

• The junctional and subserosal zones exhibit compact smooth muscle fibers and minimal extracellular matrix compared to the myometrium proper.
• The junctional zone comprises a compact and a transitional region.
• The compact region of the junctional zone directly correlates with its hypointense (low signal) appearance on T2-weighted MR images.

Conclusions:

• The compact smooth muscle composition of the junctional zone is the primary determinant of its low signal intensity on T2-weighted MRI.
• This study provides a detailed histologic correlation for uterine zonal anatomy visualized on MRI, enhancing diagnostic interpretation.