A 40-year-old woman presents with heavy menstrual bleeding (pictorial blood assessment chart score 250), dysmenorrhea, and a uniformly enlarged 14-week size uterus. Transvaginal ultrasound shows heterogeneous myometrium, myometrial cysts, and increased vascularity within the myometrium. MRI shows junctional zone maximum thickness of 16 mm with islands of endometrial glands within the myometrium. Which criterion distinguishes adenomyosis from leiomyoma on MRI?
- A Junctional zone thickness > 12 mm is specific for adenomyosis
- B Well-defined pseudocapsule and T2-hypointense signal distinguishes fibroid from adenomyosis
- C The junctional zone/myometrium ratio > 40% and heterogeneous signal are diagnostic
- D Both A and B are correct ✓
Explanation
On MRI, adenomyosis is characterized by junctional zone (JZ) maximum thickness > 12 mm (highly specific), JZ/myometrium ratio > 40%, ill-defined margins blending with the surrounding myometrium, hyperintense T2 foci (representing entrapped glands or cysts) within a T2-hypointense background, and no pseudocapsule. Leiomyomas, in contrast, are well-circumscribed, have a T2-hypointense signal throughout, possess a pseudocapsule/rim, and show mass effect. The JZ > 12 mm and the absence of a well-defined pseudocapsule together are the key distinguishing features. In practice, focal adenomyosis may coexist with fibroids and be confused on ultrasound.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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Written and medically reviewed by the StethoPrep medical team.