Co-existence of Papillary and Medullary Thyroid Carcinoma: Reports of Three Cases

Medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) are two different types of thyroid carcinoma. They have different features in terms of cellular origin, histopathology, clinical features, prevalence, and prognosis. PTC originates from follicular cells, while MTC from parafollicular cells. MTC and PTC co-existence is a rare phenomenon and occurs in less than 1% of all thyroid tumors. We report three cases with coexistent MTC and PTC in the same thyroid. The papillary component was dominant in two cases and the medullary in one case. While the first case was given radioactive iodine therapy, the third was treated with vandetanib. The second case was followed up postoperatively and did not receive treatment other than levothyroxine replacement. The co-existence of these tumors requires a different clinical approach in treatment and follow-up, depending on which type is dominant. Key Words: Mixed thyroid carcinoma, Papillary thyroid carcinoma, Medullary thyroid carcinoma.