Thyroid Collision Carcinoma: A Case Report.

Background & Objective: Thyroid cancer is one of the most prevalent endocrine neoplasms. Papillary thyroid carcinoma (PTC) and Medullary thyroid carcinoma (MTC) are two different types of thyroid cancers. The synchronous occurrence of PTC and MTC is a rare phenomenon, but it can present as a thyroid collision tumor. The purpose of this case report is to highlight a rare presentation of a collision tumor and its associated diagnostic challenges. Case Report: In this case report, a 61-year-old female patient presented with a painless anterior neck mass and voice hoarseness. She had a previous history of benign multinodular goiter and left lobectomy. Preoperative fine needle aspiration (FNA) biopsy of neck lymph nodes showed malignant epithelioid cells with anisonucleosis, plasmacytoid and spindle-like morphology, consistent with metastatic carcinoma, likely MTC. She underwent completion total thyroidectomy and histopathology investigations post-operation showed PTC in right lobe and the remnant of left lobe, and concurrent MTC was detected in two out of two central lymph nodes. On follow up patient had no signs of recurrence. Conclusion: This case highlights the importance of careful histological assessment of thyroid masses and lymph nodes for accurate diagnosis and the importance of long-term follow up after subtotal thyroidectomy or thyroid lobectomy.