A synchronous medullary and papillary thyroid carcinoma

The synchronous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) is rare (<1%). The medullary component determines the prognosis. A 31-year-old female with no relevant personal or family cancer history presented with swelling on the right side of the neck. A fine-needle aspiration biopsy was positive for MTC and PTC. Mass sequencing of 322 genes associated with cancer came back negative. The histopathological examination revealed synchronous MTC and PTC with thymic and bilateral lymph node metastasis. The patient underwent total thyroidectomy with bilateral radical neck dissection (II-V), central dissection, and mediastinal dissection including the thymus. The extent of surgery is determined by MTC and the analysis of RET and BRAF mutations. Post-operative treatment must include monitoring for specific markers (calcitonin and thyroglobulin, respectively, for MTC and PTC). Based on histopathological results and recurrent PTC, TSH suppression and iodine-131 therapy should be considered. Recurrent MTC must be treated with new targeted therapies.