Spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid with neck lymph node metastasis: a case report.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is an extremely rare type of thyroid tumor. It has been reported only 20 times in the English literature. This tumor occurs predominantly in young patients and has a protracted clinical course despite the occurrence of metastases. In the recent literature SETTLE has been considered to be a tumor of low malignant potential with distant metastases developing some years after diagnosis. Herein we report a case of SETTLE in a 22-yr-old man in which a lymph node metastasis developed soon after the primary tumor manifestation. Histological examination of the tumor showed the predominantly monophasic variant of SETTLE. The primary and metastatic lesions were highly cellular tumors composed of sheets of spindle cells that were positive for pan-cytokeratin and vimentin and negative for thyroglobulin, calcitonin, and S-100 protein.