Simultaneous occurrence of medullary and papillary thyroid microcarcinomas: a case series and review of the literature.

Introduction: Papillary thyroid microcarcinoma has been demonstrated to present in association with medullary thyroid carcinoma, however, medullary thyroid carcinoma and papillary thyroid carcinoma represent rare entities. In recent years this rarity has been increasingly observed. The pathogenesis is still controversial.