Mixed medullary-papillary carcinoma of the thyroid: a case report.

With fewer than 40 cases described in the otolaryngology literature, mixed medullary papillary thyroid carcinoma represents a rare but phenotypically distinct tumor. While isolated medullary carcinoma may be admixed with normal follicular structures, true mixed carcinoma displays morphological and immunological characteristics of medullary and papillary carcinoma within a single lesion. We report the case of a 73-year old woman initially evaluated for a multinodular thyroid goiter. The patient denied a family history of medullary thyroid carcinoma or other endocrine neoplasms. Fine needle aspiration of a nodule of the thyroid isthmus suggested a follicular neoplasm with abundant Hurthle cells and colloid present. Considering these findings, the patient underwent a left thyroid lobectomy with isthmusectomy. Histopathological analysis of the surgical specimen revealed a medullary thyroid carcinoma measuring 0.4 cm in size. Within this lesion, a distinct focus of papillary thyroid carcinoma, follicular variant, measuring 0.1 cm was also identified. Mixed medullary-papillary thyroid carcinoma is a rare clinical entity but merits consideration in the differential diagnosis of thyroid nodules particularly in patients with a family history of thyroid malignancy. The foundation of treatment of this lesion is total thyroidectomy with central compartment node dissection in the clinically N0 neck and dissection of levels II-VII in the node-positive neck.