Enlarged uterus: differentiation between adenomyosis and leiomyoma with MR imaging.

The potential of magnetic resonance (MR) imaging in differentiation of adenomyosis from leiomyoma was evaluated in 93 patients who had a palpable enlarged uterus that was suspect for leiomyoma or adenomyosis. In all cases, MR images were correlated with surgical/pathologic findings. Pathologic findings showed that 71 enlarged uteri were due to leiomyoma, including one leiomyosarcoma, and 16 were due to adenomyosis. The other six patients were shown to have an enlarged uterus attributable to simultaneous involvement of both lesions. On T2-weighted images, adenomyosis appeared as an ill-defined, relatively homogeneous low-signal-intensity area embedded with sparse high-intensity spots. In contrast, leiomyomas were well-circumscribed masses with a spectrum of signal intensity. The cause of uterine enlargement was correctly diagnosed with MR images in 92 of the 93 cases. It is concluded that MR imaging is highly accurate in helping to distinguish between adenomyosis and leiomyoma in cases of enlarged uterus.