Background: Struma ovarii, presenting as pseudo-Meigs' syndrome with an elevated CA 125 level, is a rare condition.
Case: A 65-year-old patient presented with ascites, hydrothorax, right ovarian mass, and elevated CA 125 level. These findings were suspicious for an ovarian malignancy. The mass was removed and revealed struma ovarii, a specialized ovarian teratoma composed predominantly of mature thyroid tissue. In the setting of ascites and hydrothorax, the condition is known as pseudo-Meigs' syndrome. This is the second reported case in the English language literature of pseudo-Meigs' syndrome with an elevated CA 125 level resulting from struma ovarii.
Conclusion: Struma ovarii is a rare cause of ascites, hydrothorax, and an elevated CA 125 level.