Unruptured interstitial pregnancy: a pitfall of MR imaging.

We report two cases with interstitial pregnancy, which showed completely different MR appearances. In case 1, a gestational sac was demonstrated and the diagnosis of ectopic pregnancy was straightforward. In case 2, a hypervascular mass was shown without demonstration of a gestational sac, the findings usually seen in gestational trophoblastic disease (GTD). MR imaging may play some role in the diagnosis of interstitial pregnancy when sonography is insufficient or equivocal. If GS is visualized, diagnosis is easy. However, if not, the appearance may have a spectrum and can be similar to GTD.