This is a case report of a female 1-year-old patient who complained of an increase in the volume of the tongue perceived by her mother since her first month of life, which hinted swallowing, episodes of suffocation, and injury to the onset of articulated language. Orascopy showed an increase in the bilateral sublingual volume, with softened consistency on palpation. Diagnostic and therapeutic drainage of the lesion was performed, with posterior analysis of the mucoserous aspect fluid, suggesting a benign tumor in the floor of the mouth. The patient had recurrence of the lesion after a few months. Proceeding with the diagnostic investigation, submentonian ultrasonography was performed, evidencing a cystic image with echoes, located in the topography of the sublingual glands, measuring 4.7 x 3.3 centimeters, suggestive of a plunging ranula. The patient was submitted to the surgical procedure for excision of the lesion that occurred without intercurrences.