Mixed Medullary Papillary Thyroid Carcinoma in Hyperfunctioning Hot Nodule: A Case Report and Review of the Literature

 Mixed medullary papillary carcinoma (MMPC) is a rare variant of papillary thyroid carcinoma, according to the WHO classification and it presents as a single lesion histologically composed of two distinct and intermingled neoplastic cell patterns. The histogenesis is still debatable. The lymph node metastases are usually present at the time of the diagnosis and distal metastases may appear late during follow-up. At least 13 similar lesions have been reported in the literature. We describe the case of a 61-year-old woman with a mixed medullary papillary carcinoma found in a hyperfunctioning thyroid nodule and negative pre-surgical serum calcitonin. After surgery, the patient started suppressive L-thyroxine therapy and underwent radioiodine ablation. The follow-up for both papillary and medullary components has shown no signs of persistence or recurrence of disease five years after surgery. However, the rarity of the MMPCs makes the management and the prognosis of these tumors still unclear.