Infertility: Metastatic ovarian strumosis in an in-vitro fertilization patient

Malignant struma ovarii is a very rare tumour, with considerablecontroversy concerning the necessary histologic features formalignancy. Still more infrequent is the condition termed ‘metastaticovarian strumosis’ or simply ‘benign strumosis orstrumatosis’ and characterized by the presence of peritonealimplants of mature thyroid tissue occurring in struma ovarii.‘Strumosis’ should not be confused with malignancy.Presented is a case of ‘metastatic ovarian strumosis’in a 36-year-old woman with primary infertility who underwentthree in-vitro fertilization (IVF) cycles with ovarian stimulation.She received hormonal treatment for 6 months after her lastIVF because of ‘persistent enlarged ovarian follicles’which were in fact ‘thyroid follicles’.