Off the Beaten Path: A Thyroglossal Duct Cyst in the Sublingual Space of a 31-Year-Old Male-A Case Report.

Thyroglossal duct cysts (TGDCs) are among the most common congenital anomalies of the neck, typically presenting as painless midline masses inferior to the hyoid bone. Distinguishing TGDCs from other cystic neck lesions, such as ranulas or dermoid cysts, can be challenging, particularly when they arise in uncommon locations such as the sublingual space. Here, we report an atypical presentation of a TGDC in the sublingual space of a 31-year-old Hispanic/Latino White male. The patient, with no significant medical history, presented to the emergency department at the University of California San Diego Health (Hillcrest Medical Center, San Diego, California, United States), in June 2023 after sustaining blunt facial trauma. Imaging revealed an incidental cystic lesion in the right paramedian floor of the mouth. Magnetic resonance imaging (MRI) confirmed a circumscribed cystic mass (21 × 21 × 20 mm) within the sublingual space. Imaging characteristics, including the lesion's close approximation to the hyoid bone and absence of restricted diffusion, were most compatible with a TGDC. MRI also confirmed a normal thyroid gland and no cervical lymphadenopathy. Surgical excision of the cyst, including a segment of the hyoid bone, was performed. Histopathological examination confirmed the diagnosis of a TGDC with respiratory and squamous epithelial lining. At the 1-week postoperative follow-up, flexible laryngoscopy showed no complications, with normal vocal fold function. TGDCs in the sublingual space are extremely rare, with only nine previously reported cases in the English literature. This report underscores the significance of recognizing atypical presentations of TGDCs, particularly in rare locations such as the sublingual space, expanding the understanding of their diverse clinical manifestations.