A 16-year-old male presented with a floor of mouth (FOM) mass that had been increasing in size over the past 18 months.

Eventual interference with speech and swallowing functions prompted surgical removal.

Physical examination revealed a soft cystic lesion of the FOM, with a neck component measuring 5.0 by 6.0 cm. Computed tomography (CT) and magnetic resonance imaging (MRI) of the neck showed a 6.0 cm × 5.1 cm × 6.5 cm cystic mass, bright on T2 imaging with thin peripheral enhancement, above the mylohyoid displacing the tongue musculature superiorly and posteriorly and extending inferiorly to about the hyoid bone (Figure 1).

reoperative fine-needle aspirate showed straw-colored fluid with anucleated squamous cells with no malignant cells identified.