An unusual case of struma ovarii causing ovarian torsion during pregnancy

Abstract

Struma ovarii is a rare type of ovarian teratoma characterised by a predominance of thyroid tissue. Among ovarian tumours, it accounts for 0.3% of cases and around 3% of mature cystic teratomas. It occurs mainly in the fifth and sixth decades of life. Adnexal masses are found in 1–3% of gravid women and dermoid cysts are the most common (Bernhard et al. 1999). The management of these masses in pregnancies is quite challenging, since different factors are taken into consideration, mainly the risk of malignancy, the risk of cyst rupture of torsion and the gestational age at the time of diagnosis. Struma ovarii manifests as a pelvic mass but can present as a hyperthyroid state or ascites. Histologically, it is characterised by large thyroid follicles with colloid material. The immunohistochemical staining of thyroglobulin protein confirms its thyroid nature (McCluggage and Young 2005). In undiagnosed cases undergoing surgical resection, thyrotoxicosis is a rare but potentially life-threatening complication (Matsuda et al. 2001). To-date, one case has been reported in literature of an ovarian torsion of a struma ovarii during pregnancy (Kung et al. 1990). In this report, we describe a case of a benign non-functional struma ovarii presenting as ovarian torsion during pregnancy.