Spindle epithelial tumor with thymus-like differentiation: A case report and literature review

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a rare, low-grade malignant neoplasm that mainly occurs in the thyroid gland or its perimeter. Fewer than 10 cases of SETTLE have been reported in the Chinese literature, whereas approximately 50 cases have been reported in the international literature. We report a rare case of SETTLE that occurred in the soft tissues of the neck around the thyroid gland in a 41-year-old man. The neoplastic tissue, which mainly consisted of spindle epithelial components, included sporadically visible thymus-like structures. Immunohistochemistry demonstrated CK and CK19 positivity in the thymic epithelial components and CK, vimentin, and Bcl-2 positivity in the spindle cells. Surgicalresection is the main treatment option for SETTLE. This patient underwent mass resection of the neck, and no recurrence or metastasis was observed even at 8 months postoperatively.