Spindle epithelial tumor with thymus-like elements of the thyroid: a multi-institutional case series and review of the literature.

Background/purpose: Spindle epithelial tumor with thymus-like elements (SETTLE) is a rare tumor of the thyroid observed in children and adolescents. We present a case series of 3 patients with SETTLE, focusing on the clinical and pathologic features of this rare tumor.

Methods: Three male patients presented at ages 4.5, 6.5, and 7 years with a right thyroid mass. All were treated by standard hemithyroidectomy. None had evidence of distant metastases at presentation. The diagnosis of SETTLE was confirmed at the time of the initial operation in 2 of the 3 patients.

Results: All patients had uneventful postoperative courses. Two patients remain disease-free 4 and 7 years postresection, respectively. One patient presented 10 years after resection with shortness of breath and hemoptysis secondary to multiple bilateral parenchymal lung metastases. This patient received chemotherapy against the epithelial components of the tumor with a 25% response based on imaging studies.

Conclusion: Spindle epithelial tumor with thymus-like elements is rare tumor that should be suspected if spindle elements are observed in the resected thyroid specimen. Because these patients may present with delayed metastases, follow-up is recommended. However, chemotherapy against specific tumor elements is only marginally effective.