Extensive Teratoid Cyst in the Floor of the Mouth of a 12-Month-Old Infant: A Case Report

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Abstract Dysontogenic cysts (DCs) are uncommon developmental lesions encompassing three related histological entities: dermoid cyst, epidermoid cyst, and teratoid. Although benign, DCs are rare in the oral cavity, with an estimated incidence of 1.6%, and most frequently affect the floor of the mouth due to its role in embryonic fusion. Clinically, they present as painless, slow-growing, and progressive swelling, which may interfere with vital functions such as swallowing, speech, mastication, and breathing. Despite their congenital origin, diagnosis typically occurs between the second and third decades of life due to the variability in clinical presentation. We report a rare case of an extensive teratoid cyst in the floor of the mouth of a 12-month-old infant. The patient was referred to the Oral and Maxillofacial Surgery service with a history of progressive swelling in the region since the age of four months, associated with breastfeeding difficulties and signs of partial upper airway obstruction during sleep. An excisional biopsy under general anesthesia was performed via an intraoral approach. Microscopic analysis revealed a cystic cavity lined by non-keratinized stratified squamous epithelium, with variable thickness and focal areas of thickening. The stroma was composed of dense connective tissue and skeletal striated muscle fibers, including juxtaepithelial fibers, which led to the diagnosis of teratoid cyst. The patient has been followed up for nine months postoperatively, with no evidence of recurrence or reports of other clinical complaints.