Imaging of gynecological disease (4): clinical and ultrasound characteristics of struma ovarii

Objectives: To describe the clinical history and ultrasound findings in women with struma ovarii.

Methods: Women with a histological diagnosis of struma ovarii who had undergone preoperative ultrasound examination were identified from the databases of five ultrasound centers. The tumors were characterized on the basis of ultrasound images, ultrasound reports and research protocols (when applicable) using the terms and definitions of the International Ovarian Tumor Analysis (IOTA) group. In addition, four authors reviewed all ultrasound images and described them using pattern recognition.

Results: Of 31 patients identified, 16 had pure struma ovarii (one malignant), whereas in 15 patients the struma ovarii were 'impure', constituting the major part of a dermoid cyst (all benign, bilateral in one case). Median age was 40 (range, 18-80) years and 22 (71%) patients were of fertile age. Thirteen patients (42%) were asymptomatic, nine (29%) presented with pain, six (19%) with bloating, two (6%) with irregular bleeding and one (3%) with thyreotoxicosis. Most pure struma ovarii (11/16 cases, 69%) contained solid components, but cystic components were always present. The color content at Doppler examination varied from none to abundant. Four patients had ascites. Using pattern recognition the most specific feature of pure struma ovarii was the 'struma pearl', i.e. a smooth roundish solid area, similar, but not identical, to the 'round white ball' seen in dermoid cysts. 'Struma pearls' were present in six cases of pure struma ovarii. Most (10/16, 63%) cases of impure struma ovarii manifested ultrasound features compatible with a dermoid cyst, but six manifested ultrasound features similar to those of pure struma ovarii, 'struma pearls' being seen in three of these.

Conclusions: The sonographic features of struma ovarii vary. Struma ovarii may be suspected when a 'struma pearl' is seen. Whether 'struma pearls' are indeed a specific ultrasonographic feature of struma ovarii needs to be determined in a prospective study.