Chemosensitivity in Carcinoma Showing Thymus-Like Differentiation: A Case Report and Review of the Literature

Background: Carcinoma showing thymus-like differentiation (CASTLE) is an extremely rare malignant neoplasm of the thyroid that originates from ectopic thymic tissue. No sufficient evidence exists regarding the efficacy of chemotherapy for cases with distant metastases or advanced disease because of the rarity of the disease itself. Patient: We report a case of CASTLE with lung metastasis that showed good responses to first-line (cisplatin, doxorubicin, vincristine, and cyclophosphamide) and second-line (carboplatin and paclitaxel) chemotherapies. Summary: This is the first case of CASTLE reported to show a good response to two serial chemotherapies. Conclusion: This case suggests that CASTLE is a chemosensitive tumor and that chemotherapy should be attempted in patients with advanced or metastatic CASTLE.