Struma ovarii: appearance on MR images.

Background: The purpose of this multi-institutional study was to examine the appearance of struma ovarii on magnetic resonance (MR) images.

Methods: MR images of 12 patients with histologically proven struma ovarii were retrospectively reviewed. All patients underwent T1-weighted and T2-weighted imaging. Contrast-enhanced T1-weighted images with Gd-DTPA were available in 10 patients. The following determinations were made: tumor morphology, signal intensities, contrast-enhancement effects of solid components with Gd-DTPA, and comparison of MR images with resected specimens.

Results: All 12 patients had both cystic and solid components, with a multilobulated surface and thickened septa. Signal intensities on T1-weighted images were mainly low, partly intermediate to high, or high, and those on T2-weighted images were mainly high, with different signal intensities. Contrast-enhancement effects were marked or moderate. The contents that showed low signal intensities on T1-weighted images and signal voids or low signal intensities on T2-weighted images were viscid gelatinous materials.

Conclusions: A multicystic tumor with a solid component, a multilobulated surface, and signal intensities that indicate the presence of viscid gelatinous materials appear to be a characteristic MR finding of struma ovarii.