Imaging in gynecological disease (24): clinical and ultrasound characteristics of ovarian mature cystic teratomas.

OBJECTIVE: To describe the clinical and ultrasound features of ovarian mature cystic teratomas (MCTs). METHODS: This was a retrospective study. From the International Ovarian Tumor Analysis (IOTA) database, we identified patients with a histologically confirmed diagnosis of MCT who had undergone transvaginal ultrasound examination between 1999 and 2016 (IOTA phases 1, 2, 3 and 5) in one of five centers. Ultrasound was performed by an experienced examiner who used the standardized IOTA examination technique and terminology. In addition to extracting data from the IOTA database, available two-dimensional grayscale and color or power Doppler images were reviewed retrospectively to identify typical ultrasound features of MCT described previously and detect possible new features using pattern recognition. All images were reviewed by two independent examiners and further discussed with two ultrasound experts to reach consensus. RESULTS: Included in the study were 454 patients with histologically confirmed MCT. Median age was 33 (range, 8-90) years and 66 (14.5%) patients were postmenopausal. Most MCTs were described by the original ultrasound examiner as unilocular (262/454 (57.7%)) or multilocular (70/454 (15.4%)) cysts with mixed echogenicity of cystic fluid (368/454 (81.1%)), acoustic shadowing (328/454 (72.2%)) and no or little vascularization on color Doppler (color score 1, 240/454 (52.9%); color score 2, 123/454 (27.1%)). The median largest lesion diameter was 66 (range, 15-310) mm. A correct preoperative diagnosis of MCT was suggested by the original ultrasound examiner in 372/454 (81.9%) cases. On retrospective review of ultrasound images of 334 MCTs that had quality sufficient for assessment, 'dots and/or lines' and/or 'echogenic white ball' (typical features according to the literature) were present in 271/334 (81.1%) masses. We identified four new ultrasound features characteristic of MCT: 'cotton wool tufts', 'mushroom cap sign', 'completely hyperechogenic lesion' and 'starry sky sign'. At least one classical or novel ultrasound feature was present in 315/334 (94.3%) MCTs. Twenty-nine (8.7%) MCTs manifested vascularized solid tissue, of which seven exhibited no typical features. CONCLUSION: We provide a comprehensive overview of conventional and newly described ultrasound features of MCTs. Only a small proportion of MCTs did not manifest any of the typical features. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.