Papillary thyroid carcinoma in thyroglossal duct cyst: a Peruvian case series.

Summary: Papillary thyroid carcinoma (PTC) is the most frequent type of differentiated thyroid cancer, while thyroglossal duct cysts (TGDCs) are common congenital anomalies of the neck. The coexistence of PTC within a TGDC is exceptionally rare, with a reported incidence of less than 1.5%. We present three Peruvian cases of PTC arising in TGDCs. The patients (two females and one male; age range: 34-47 years) presented with progressive midline cervical masses of two to four years' duration. All underwent cervical ultrasound, contrast-enhanced computed tomography, and fine-needle aspiration biopsy. Histopathology confirmed PTC, including classical and follicular variants. Surgical management varied: two patients underwent Sistrunk procedure alone, while one required Sistrunk surgery followed by total thyroidectomy, cervical lymph node dissection, and radioactive iodine (RAI) therapy. All patients remain disease-free after 6-12 years of follow-up. The diagnosis of carcinoma in TGDC is often incidental, but preoperative imaging and cytology can raise suspicion. Optimal management remains controversial; while the Sistrunk procedure may be sufficient in most cases of PTC confined to TGDC without extracapsular extension, in some scenarios, such as the presence of suspicious thyroid nodules, extracystic extension, and cervical lymph node metastasis, an additional thyroidectomy and RAI therapy may be warranted. In conclusion, PTC in TGDC is a rare entity with generally favorable prognosis. Early recognition, individualized treatment, and multidisciplinary decision-making are essential for optimal outcomes. Learning points: Suspect malignancy in any persistent or enlarging midline neck mass, especially when imaging shows solid components or calcifications. FNAB may have variable diagnostic yield in cystic lesions due to low cellularity; accuracy can be improved by aspirating cystic contents first or targeting the solid components of the cyst. Treat with the Sistrunk procedure, adding total thyroidectomy and/or radioiodine based on oncologic risk and nodal involvement. Expect a generally favorable prognosis, but maintain long-term surveillance given the (low) risk of recurrence. Guidelines regarding management of thyroglossal duct cyst cancer have recently been included within ATA 2025 thyroid cancer guidelines.