Successful Management of a Patient with Malignant Thyroid Teratoma

Background: Malignant thyroid teratomas are rare tumors with a poor prognosis. Little is known about their pathogenesis or treatment. Here, the case is reported of an adult woman with an aggressive thyroid teratoma with primitive neuroectodermal tumor (PNET) malignant transformation, successfully managed with neoadjuvant chemotherapy and surgery. Patient Findings: Sequencing of paired tumor and normal tissues revealed a DICER1 c.5438A>G (p.E1813G) somatic mutation in 56% of sequencing reads consistent with a driver event. Summary and Conclusions: To the authors' knowledge, DICER1 mutations have not been previously reported in teratomas but have been described in PNETs, suggesting a role in the malignant transformation of this case.