Conversion surgery after lenvatinib treatment for anaplastic thyroid carcinoma: a case report.

[BACKGROUND] Anaplastic thyroid carcinoma (ATC) is the most aggressive form of thyroid carcinoma. Lenvatinib, a multikinase inhibitor, is rarely used in preoperative settings due to adverse effects including delayed wound healing and fistula formation. Herein, we report the use of lenvatinib treatment prior to conversion surgery for the treatment of ATC.

[CASE PRESENTATION] A 71-year-old woman was referred to our hospital with suspected thyroid cancer with recurrent laryngeal nerve invasion and cervical lymph node metastasis based on the results of ultrasonography. Computed tomography demonstrated the presence of a thyroid tumor invading the trachea and esophagus with no evidence of distant metastasis. Fine needle aspiration of the left cervical lymph node indicated the lymph node metastasis of ATC. As the tumor had widely invaded the trachea and esophagus, unresectable ATC was diagnosed and treatment with lenvatinib was initiated at a dose of 24 mg/day. On day 13 of lenvatinib treatment, the primary tumor and lymph node metastases demonstrated a partial response to therapy. As the tumor was now considered resectable, the decision was made to perform conversion surgery. Total thyroidectomy and left lateral neck node dissection were performed 7 days after the withdrawal of lenvatinib. The patient was discharged on postoperative day 5 with no complications. Histopathological examination demonstrated that the tumor contained the component of papillary thyroid carcinoma, squamoid ATC cells, and granulation tissue. In areas of granulation tissue, atypical cells with spindle-shaped or polygonal morphology, pyknotic nuclei, and scant cytoplasm were observed. Immunohistochemically, these cells were positive for cytokeratin AE1/AE3, TTF-1, and p53 and negative for thyroglobulin and PAX8. Therefore, the areas of granulation tissue observed within tumor samples were also considered ATC that were affected by lenvatinib treatment. In total, approximately 50% of resected tumor comprised ATC, and 70% of them had been changed to granulation tissue.

[CONCLUSIONS] The findings in the present case indicate that lenvatinib may have significant antitumor effects in preoperative settings. Lenvatinib may represent a promising candidate therapy for unresectable ATC by increasing tumor resectability.