Adenomyosis and leiomyoma: differential diagnosis with MR imaging.

To assess the capability of magnetic resonance (MR) imaging to enable differentiation of adenomyosis from leiomyoma, a prospective study was performed in 21 premenopausal patients with a strong clinical suggestion of adenomyosis. Histologic findings from hysterectomy (19 patients) and biopsy specimens (two patients) showed that eight patients had adenomyosis (three focal, five diffuse) and 12 had leiomyomas (five of the 12 also had microscopic foci of adenomyosis); one patient had a normal uterus. All eight cases of adenomyosis were correctly diagnosed from MR images. On T2-weighted MR images, diffuse adenomyosis appeared as a thickening of the junctional zone, whereas focal adenomyosis appeared as a low-signal-intensity mass poorly marginated from the adjacent myometrium. Ten of the 12 leiomyomas were correctly diagnosed from MR images. In the other two cases of leiomyoma, differentiation between focal adenomyosis and leiomyoma was not possible. Microscopic foci of adenomyosis were not demonstrated with MR imaging.