Metastatic follicular thyroid carcinoma with clear cell component mimicking neuroendocrine tumor: Case report

Abstract

Follicular thyroid carcinoma with a clear cell component is a rare tumor with unknown malignant potential. We introduce a case of follicular thyroid carcinoma with a clear cell component and focal neuroendocrine features, which presented as a metastatic focus in the T10 vertebra.A 62-year-old male patient presented with chronic back pain, bilateral lower leg weakness, and numbness, in conjunction with a radiologically identified spinal lesion at the level of T10. Both the cytology and histology of the 4.4 cm T10 spinal lesion revealed a neuroendocrine tumor of uncertain primary origin. The immunohistochemical profile showed that the tissue of origin could be kidney, lung, thyroid, and gastrointestinal. Ultrasound-guided fine-needle aspiration of the 2.2 cm solid thyroid nodule was performed, showing an identical clear cell cytomorphology to that of the spinal lesion. The immunophenotype was consistent with primary thyroid origin.We report a follicular thyroid carcinoma with a clear cell component that presented as a metastatic lesion to the bone.