Unusual spindle cell tumor of thyroid (SETTLE).

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a rare tumor seen mostly in children and adolescents. It is presumed that it arises from ectopic thymus or remnants of branchial pouches that differentiate along the thymic line. Unusual spindle cell-predominant histology makes this entity difficult to recognize. The clinical course is not exactly known due to the small number of reported cases but metastasis has been documented during initial presentation. We report a case of SETTLE in the neck where preoperative clinical and radiological impression was that of a mass in the left submandibular gland area. However, during the operation it was felt by the surgeon that the mass was in continuity with the left thyroid lobe.