Thyroid Gland Spindle Epithelial Tumor with Thymus-Like Elements

**Semantic type:** Neoplastic Process

**Definition:** A rare, slow growing malignant tumor of the thyroid gland arising from intrathyroidal thymic tissue. It is characterized by a lobulated architectural pattern and the presence of a biphasic cellular population composed of spindle epithelial cells and glandular cells. A small number of cases are composed exclusively of spindle epithelial cells or glandular cells.

**Synonyms:** - SETTLE - SETTLE - Spindle Epithelial Tumor with Thymus-Like Elements - Thyroid Gland Spindle Cell Tumor with Thymus-Like Differentiation