Coexistence of Papillary and Medullary Thyroid Carcinoma: A Rare Entity

Introduction Papillary thyroid carcinoma (PTC) are the most common of all thyroid cancers (>70%). It originates from follicular thyroid cells and shows multifocal growth in nearly 29% cases. Immunohistochemical results of PTC are positive for thyroglobulin and Thyroid Transcription Factor-1 (TTF-1). PTC cells are negative for calcitonin, Carcinoembryonic Antigen (CEA), and chromogranin. PTC The coexistence of different types of thyroid carcinomas is rather unusual. It has been considered coincidental and linked to the growing incidence of papillary thyroid carcinoma (PTC). This paper presents a case of multifocal PTC and coexistent medullary thyroid carcinoma (MTC) distinct from each other, along with PTC lymph node metastasis. The 44year-old female patient underwent subtotal thyroidectomy with a pre-operative diagnosis of multinodular goiter. Histological reports revealed PTC in the right lobe and PTC beside a tumoral area morphologically suspicious for MTC in the left thyroid lobe. Immunohistochemistry confirmed the diagnosis of MTC. Post-operative ultrasound and subsequent fine needle aspiration biopsy revealed lymph node metastases of PTC in the right anterior cervical area. Complementary thyroidectomy, central neck dissection, and right modified neck dissection were carried out with subsequent I-131 ablation therapy. In conclusion, the biological behaviors and prognoses of MTC and PTC are different. Therefore, the entity demands a different clinical approach in treatment and follow-up.