Uterine Pathology
Overview
Benign uterine pathology is a leading cause of menorrhagia and pelvic pain. The most important entities are leiomyomas (fibroids) and adenomyosis, both with characteristic imaging appearances enabling non-invasive diagnosis.
Leiomyomas (Fibroids)
Fibroids are oestrogen-dependent benign monoclonal smooth muscle tumours. They are classified by the FIGO system based on their relationship to the endometrial cavity:
- Submucosal (FIGO 0-2): Project into the endometrial cavity. Most strongly associated with menorrhagia, subfertility, and pregnancy loss.
- Intramural (FIGO 3-4): Entirely within the myometrial wall. Most common type overall.
- Subserosal (FIGO 5-7): Project from the serosa. Can become pedunculated and undergo torsion.
Fibroid Degeneration on MRI
- Hyaline (most common, 60%): T1 isointense, T2 hypointense. Homogeneous.
- Cystic: T2 hyperintense foci within the fibroid.
- Red (Carneous): Haemorrhagic infarction in pregnancy. T1W hyperintense peripheral rim. Acute severe localised pain.
- Calcific: Low signal on all MRI sequences. Peripheral ring of calcification visible on CT/plain film.
WarningAdenomyosis vs Fibroids on MRI
Adenomyosis = ectopic endometrial glands within the myometrium. MRI hallmarks: junctional zone thickness >12 mm, T2 hypointense islands within the myometrium, and diffuse low-signal thickening. Unlike fibroids, it is diffuse and cannot be surgically resected (hysterectomy is definitive).
High Yield Facts
LightbulbFRCR / MD Prep Pearl
Malignant transformation of a fibroid into a leiomyosarcoma is exceptionally rare (<0.5%). Suspect if rapid growth occurs post-menopause. MRI cannot reliably distinguish the two — tissue diagnosis is required. Leiomyosarcoma typically shows heterogeneous signal, ill-defined margins, and central necrosis.