Background: Leiomyomas represent the most common benign uterine tumors. Typically asymptomatic, they may determine menometrorrhagia, abdominal pain and infertility. They may be singular or multiple and may have variable size. When leiomyomas increase in size, their vascular supply may become insufficient determining different types of degeneration: hyaline, myxoid, cystic and hemorrhagic (red). Differential diagnosis includes adenomyosis, solid adnexal masses, focal contraction of myometrium and leiomyosarcomas of the uterus. Our purpose is to describe MR imaging findings, histological features and clinical aspects of uterine leiomyomas.

Materials and Methods: Our MR protocol includes sagittal, oblique coronal, oblique axial T2-weighted fast spin-echo and T1-weighted 3D gradient echo LAVA fat-suppressed sequences before and after contrast administration, and axial DWI SE EPI sequence.

Results: Non-degenerated uterine leiomyomas typically appear as well defined masses, homogeneously hypointense in comparison to the surrounding myometrium on T2-weighted images and with intermediate signal intensity on T1-weighted images. Hypercellular leiomyomas show signal intensity higher than that of non degenerated leiomyomas on T2-weighted images and present contrast enhancement after administration of mdc. Degenerated leiomyomas present variable signal intensity on T2-weighted images and on T1-weighted images obtained before and after contrast administration. Differential diagnosis with leiomyosarcoma, characterized by hemorragic areas, necrosis and, frequently, irregular margins may be difficult and sometimes only possible with histopathology.

Conclusions: MRI is the most accurate radiological tool in detection and localization of uterine leiomyomas. Leiomyomas characterization, often possible with MR imaging, require knowledge of pathological features and imaging findings associated with the different kinds of degeneration. MRI is an irreplaceable tool in planning the correct therapeutic strategy and in follow up after therapy.