Control of Lung Metastases and Colon Polyposis with Lenvatinib Therapy in a Patient with Cribriform-Morular Variant of Papillary Thyroid Carcinoma and an APC Gene Mutation: A Case Study.

Background: The cribriform-morular variant (CMV) is a rare subtype of papillary thyroid carcinoma (PTC), and is often associated with familial adenomatous polyposis (FAP). This variant is generally indolent, but some aggressive cases have been reported. Patient Findings: We present the case of a 24-year-old woman who underwent total thyroidectomy with prophylactic central lymph node dissection and modified radical neck dissection for CMV-PTC. No distant metastases were identified preoperatively. However, multiple large lung metastases were detected three and half years after surgery. She also had FAP with a germline APC gene mutation. Summary: She was started on lenvatinib because of the metastatic disease. One month after the initiation of lenvatinib (24 mg), her lung metastases reduced significantly. She has continued lenvatinib for 24 months (present dose, 10 mg). The lung metastases have not progressed during this period. Only a few small polyps were newly detected on endoscopy after lenvatinib administration. This number was considerably higher before therapy, when an average of 21-75 polyps were resected at each endoscopy session. Conclusions: This is the first report of the use of lenvatinib for the treatment of distant metastases from CMV-PTC. In addition to the efficacy in treating metastatic lesions of this rare variant of PTC, lenvatinib shows promise in the management of associated FAP. This treatment strategy may be useful in the management of recurrent CMV-PTC and in those with FAP who refuse colectomy.