Papillary Carcinoma of Lateral Thyroglossal Duct Cyst with De Novo Papillary Carcinoma of Thyroid: A Rare Case Report.

Thyroglossal duct cysts are commonly seen in the midline of the neck, accounting for 7% of cases presenting with midline swelling. Carcinoma within a thyroglossal duct cyst is extremely rare, occurring in fewer than 1% of cases, and lateral occurrences are particularly uncommon. This case describes a 25-year-old female with papillary carcinoma identified in the left lateral thyroglossal duct cyst, along with de novo papillary carcinoma in the right thyroid lobe.