PRIMARY PAPILLARY CARCINOMA ARISING IN A THYROGLOSSAL DUCT CYST SIMULATING A CYSTIC LYMPHANGIOMA: A Case Report With Literature Review

Background: Lateral cervical cystic masses in adults pose a diagnostic challenge, the majority being benign. Papillary thyroid carcinoma (PTC) arising in a thyroglossal duct cyst (TGDC) is rare and can mimic benign lesions, leading to mismanagement. 

Case Presentation: A 34-year-old man with no significant medical history presented with a right lateral cervical mass evolving over 7 years. Ultrasound-guided fine-needle aspiration suggested a cystic lymphangioma. Cervicothoracic MRI revealed a large bilobed cystic formation (150 × 90 × 66 mm) with a central enhancing solid component (23 × 13 × 10 mm). The lesion displaced adjacent structures without evidence of invasion. Surgical excision revealed unexpected histology of PTC. Subsequent work-up identified an atrophic thyroid gland and a juxta-hyoid solid mass. Total thyroidectomy combined with Sistrunk procedure confirmed a primary PTC arising in a TGDC, without intrathyroidal tumor foci. 

Conclusion: This case emphasizes the need for systematic suspicion of malignancy in any cervical cystic mass containing a solid component, regardless of initial cytology. Primary PTC arising in a TGDC, although rare, should be included in the differential diagnosis to guide appropriately oncologic surgical management. 

Keywords: Papillary thyroid carcinoma; Thyroglossal duct cyst; Cystic cervical mass; Cystic lymphangioma; Diagnostic pitfall.