Background: Malignant struma ovarii is a rare tumor, consisting of a struma ovarii with malignant transformation. The association of a malignant struma ovarii with pseudo-Meigs' syndrome and elevated Ca-125 levels has been never reported.
Case: A 66-year-old woman presented with monolateral ovarian mass, ascites, hydrothorax, and elevated Ca-125 levels. Optimal medical staging was performed. Definitive histological examination revealed a malignant struma ovarii. The immediate and complete resolution of symptoms and rapid decline of both Ca-125 and thyroglobulin levels to normal value were achieved post-operatively. After counseling, strict follow-up was planned, and no adjuvant therapy was administered.
Conclusion: We report the first case of pseudo-Meigs' syndrome associated with malignant struma ovarii and elevated Ca-125 levels. The choice of not performing adjuvant therapy is feasible after optimal surgery and adequate staging procedure given to the usually clinical benign course and the low incidence of metastases in malignant struma ovarii. Careful patient counseling is required.