Struma ovarii: role of imaging?

As clinical features in struma ovarii patients in the absence of thyrotoxicosis are generally non-specific and resemble ovarian malignancy, preoperative radiological diagnosis becomes all the more relevant in order to avoid ovarian cancer type surgery (including bilateral salpingo-oophorectomy, hysterectomy, omentectomy and occasionally appendectomy) for this usually benign and rare ovarian mass. As struma ovarii is an uncommon entity, it is all the more important to perform state-of-the-art magnetic resonance (MR) imaging, including high-resolution imaging and diffusion-weighted imaging. The goal of this review paper is to give an update of the key findings of both benign and malignant struma ovarii and to present an unusual case of a purely cystic ovarian struma. Key Points • Clinical features in struma ovarii are generally non-specific and resemble ovarian malignancy.• Pre-operative radiological diagnosis is important to avoid ovarian cancer type surgery (bilateral salpingo-oophorectomy, hysterectomy, omentectomy and occasionally appendectomy).• State-of-the-art MR imaging might help to characterise this unusual ovarian mass.• Struma ovarii can occasionally present as a purely cystic lesion.• However, the role of imaging to identify struma ovarii preoperatively remains limited.