Background: Struma ovarii is a monodermal teratoma that usually presents as a solid pelvic mass. Occasionally the lesions are cystic. Rare cases present with ascites or pseudo-Meigs' syndrome. The association of a cystic struma ovarii with ascites and an elevated CA-125 level is exceptionally rare.
Case: A 51-year-old woman presented with ascites and a cystic pelvic mass. There was marked elevation of her CA-125 level. The clinical impression was ovarian carcinoma. Frozen section revealed a multicystic struma ovarii.
Conclusion: Struma ovarii can mimic ovarian carcinoma clinically, particularly if cystic and associated with ascites and an elevated CA-125 level.