A Rare Collision in Thyroid and Lymph Node: A Case Report and Review of Literature.

Synchronous papillary and medullary thyroid carcinomas are exceptionally rare. This case report describes a 13-year-old girl with familial medullary thyroid cancer linked to germline rearranged during transfection (RET) proto-oncogene mutation, with a high risk of early onset and aggressive disease, who underwent total thyroidectomy with prophylactic neck dissection. Histopathology revealed distinct papillary and medullary thyroid cancers in separate thyroid lobes, which was a type IV synchronous tumor, with one lymph node showing metastatic deposits from both tumors. This case highlights the rare occurrence, diagnostic challenges of such dual malignancies, emphasizing the need for genetic testing and vigilant long-term follow-up.