Extrathyroid carcinoma showing thymus-like differentiation (CASTLE): a new case report and review of the therapeutic role of neck dissection and radiotherapy.

We present here a case of extrathyroid CASTLE (the third case reported in the English literature) treated with excision and neck dissection without radiotherapy. Also, we reviewed the literature and analyzed the therapeutic results of each treatment modality for CASTLE. A 27-year-old male had initially presented with a painless, right neck mass for 2 months. Computed tomography of the neck showed a 3.8 × 3.2 × 3.8 cm heterogeneously enhancing mass at right level IIa, and no definite thyroid lesion was found. An excisional biopsy was done and the pathologic diagnosis was CASTLE. Then we performed a right modified radical neck dissection and right thyroid lobectomy. After three years, no evidence of tumor recurrence was noted. Total excision followed by neck dissection could be a sufficient surgical treatment option for CASTLE. Postoperative radiotherapy might be an alternative treatment option for neck dissection in patients with positive nodal status.