Intranodular Thyroid Metastasis of a Large Cell Neuroendocrine Carcinoma of the Endometrium

Abstract A 64-year-old woman underwent initial 18 F-FDG PET/CT staging for a suspicious endometrial mass, which showed high uptake in the endometrial mass and a focal uptake in a known left thyroid nodule. Histology revealed a high-grade large cell neuroendocrine carcinoma of the endometrium with FIGO (International Federation of Gynecology and Obstetrics) stage Ib. Further explorations revealed a synchronous thyroid metastasis. Patient then received adjuvant immunochemotherapy. This case showed a potential pitfall in the initial assessment of this rare and aggressive malignancy on which the therapeutic approach greatly depends.