Background
Uterine leiomyomas (myomas, fibroids) are the most common benign tumors of the female genital tract. They arise from the smooth muscle cells and fibroblasts of the myometrium. Occurring in 20% – 30% of women of reproductive age. Most leiomyomas are asymptomatic, although patients may present with abnormal uterine bleeding or bulk-related symptoms. It is important to differentiate a leiomyosarcoma from a leiomyoma. Myomectomy is the surgical removal of fibroids without removing the uterus. Uterine artery embolization is a new procedure aimed at preventing the need for major surgery.
Educational Goals / Teaching Points
Understand the different degeneration types and most common associated findings. Review common and uncommon leiomyoma imaging findings on MRI. Discuss spectrum of fibroid degeneration and imaging characteristics.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
MRI is the most effective modality for accurately characterizing pelvic masses. It has been shown to be more sensitive in identifying uterine fibroids than US, it does not involve the use of ionizing radiation, and it can readily demonstrate the uterine zonal anatomy. Non-degenerated uterine leiomyomas typically appear as well defined masses, homogeneously hypointense in comparison to the myometrium on T2WI and with intermediate signal intensity on T1WI. Degenerated leiomyomas present variable signal intensity on T2WI and on T1WI obtained before and after contrast administration.
Conclusion
Fibroids are the most common uterine neoplasm. Pelvic MRI has been shown to be the best imaging method for the characterization of leiomyomas, allowing to identify the different types of degeneration. Typical imaging features of uterine fibroids include low to intermediate T1, low T2 with variable enhancement. Differentiation between leiomyoma degeneration and leiomyosarcoma is a diagnostic challenge.
