Ranula vs. Atypical Sublingual Branchial Cleft Cyst: A Case Report

Congenital cystic lesions in the floor of the mouth in infants present significant diagnostic challenges owing to overlapping clinical and radiological features. We report a rare case of a one-year-old boy with a gradually enlarging, painless left sublingual swelling noticed since birth. Clinical examination revealed a soft, fluctuant 3 × 4 cm mass that did not move with deglutition or tongue protrusion, along with a small midline submental dimple. Contrast-enhanced computed tomography (CECT) showed a well-defined, non-enhancing cystic lesion (4.1 × 2.1 × 3.9 cm) in the left sublingual space, compressing adjacent muscles without extension to the hyoid bone or submandibular gland. A provisional diagnosis of plunging ranula was made preoperatively. The lesion was completely excised via an intraoral approach. Intraoperatively, thick yellow fluid and a fistulous tract extending toward the submental dimple were noted. Histopathology demonstrated a cyst lined by pseudostratified columnar respiratory epithelium in some areas and stratified squamous epithelium in others, with no thyroid tissue present-findings consistent with an atypical sublingual branchial cleft cyst (likely of second branchial pouch origin) associated with a sinus tract rather than a simple or plunging ranula. The postoperative course was uneventful, with no recurrence at six-month follow-up. This case underscores the rarity of branchial cleft remnants manifesting as isolated sublingual cysts in infancy and highlights the importance of complete surgical excision, including any associated sinus tract, to prevent recurrence. It also illustrates the limitations of preoperative imaging in definitively distinguishing ranula from atypical branchial anomalies in young children.