Malignant struma ovarii: Advances in molecular pathogenesis, classification, diagnosis and treatment

Malignant struma ovarii (MSO) is an extremely rare ovarian teratoma containing malignant thyroid tissue, typically presenting in middle‐aged women. Molecularly and histologically, MSO mirrors thyroid carcinoma and includes analogous subtypes as defined in the 2022 WHO classification: ‘BRAF‐like’ tumours (commonly driven by BRAF^V600E mutations or kinase fusions) and ‘RAS‐like’ tumours (driven by mutations in the RAS pathway), along with rare high‐grade variants with aggressive behaviour. Next‐generation sequencing shows that MSO harbours a mutational spectrum closely matching primary thyroid cancers. Genotype‐guided targeted therapies (e.g. BRAF/MEK inhibitors, selective RET or NTRK inhibitors and multikinase inhibitors) are emerging as promising options for advanced or radioiodine‐refractory cases. Surgical excision of the ovarian tumour is typically curative for localized disease. Thyroidectomy followed by radioactive iodine (RAI) is reserved for high‐risk tumours. Long‐term surveillance is essential, as late recurrences can occur. In this first comprehensive review of MSO, we integrate our own case series findings with published data to provide an up‐to‐date synthesis of its clinicopathologic spectrum and management.