Neuroendocrine Carcinoma of the Uterine Cervix With Metastases to the Thyroid Gland: A Case Report and Clinical Pathological Review.

Thyroid metastasis from a neuroendocrine carcinoma (NEC) is atypical, and the most common site of origin is the lung. We present the case of a 48-year-old lady with a history of NEC in the uterine cervix, classified initially as a p16-positive high-grade endocervical adenocarcinoma with endometrioid differentiation in a cervical biopsy. The patient, after having a thyroid ultrasound due to thyroid nodules, showing a multinodular goiter and suspicious nodules, and a subsequent fine-needle aspiration with a diagnosis of papillary thyroid carcinoma, presented to our hospital for a total thyroidectomy. Histologically, there were metastatic high-grade carcinoma foci within the thyroid, consistent with metastasis from the cervical primary tumor based on the morphology and immunohistochemical stains, the tumor was re-classified as an NEC. The thyroid gland is an uncommon site for metastasis from primary sites, and a very rare site for an NEC origin; besides, this tumor type is infrequent in the uterine cervix and bears an unfavorable prognosis when present. Therefore, when encountering a high-grade metastatic tumor within the thyroid, an NEC has to be considered in the differential diagnosis for a prompt diagnosis and an appropriate treatment.