To investigate the MRI features of ovarian theca fibroma (OTF) and compare it with histopathology features in order to improve the accuracy of OTF diagnosis.

The clinical data of 33 patients with OTF which were confirmed by surgical pathology from January 2005 to December 2016 were analyzed retrospectively. The signal characteristics and intensities of MRI were compared with histopathology features.

The lump largest diameter of 33 patients with OTF was 2.5 to 18.0 (6.65 ± 4.46) cm. The substantial lump was in 22 cases. T₂WI and T₂WI fat suppression imaging showed a low or equal mixed signal among which there was slightly high or high signal, and T₁WI imaging showed relatively uniform low signal. The cystic and solid lump was in 11 cases, including 7 cases of solid lumps and 4 cases of cystic-solid lumps, T₂WI and T₂WI fat suppression imaging of solid area showed equal or low signal among which there were a small patchy high or slightly high signal, and T₂WI and T₂WI fat suppression of cystic areas showed high signal; T₁WI of solid and cystic areas showed uniform low signal. Enhanced appearance: in the 33 cases of enhancement, the parenchyma part showed mild enhancement, of which 14 cases were equal enhancement, 19 cases were uneven enhancement. During the arterial phase, all of 33 cases showed mild enhancement; 15 cases were obviously enhanced and 18 cases were mildly enhanced in the portal vein phase; 21 cases remained enhanced and the enhanced intensity of 12 cases decreased in the delayed phase. Comparison of histopathology features with MRI features showed that there were a higher proportion of fibrous cells under the microscope in 22 cases of parenchymal tumor, in which the fat suppression image of T₂WI and T₂WI showed equal or low signal in parenchyma, and T₁WI showed even low signal; and there were a higher proportion of tumor cells and less collagen fibers under the microscope in 11 cases of cystic-solid tumor, in which the T₂WI showed a slightly equal and higher signal and T₁WI showed low signal in parenchyma.

The MRI features have some characteristics, such as low and equal signal of T₂WI in parenchyma, mild enhancement during arterial phase and continuous enhancement in portal vein and delayed phase, which is helpful for diagnosis of OTF.

Ovarian neoplasms; Fibroma; Magnetic resonance imaging; Pathology; Retrospective studies