Dermoid cyst is a developmental anomaly, which is rarely seen in paediatric population. Its occurrence in the floor of mouth is relatively uncommon accounting to about 0.01 % of all oral lesions and oral cavity dermoid cyst constitute 1.6 % of all body dermoids. They usually present as asymptomatic swelling, showing slow and progressive growth, sometimes involving more than one anatomical areas. It occurs as a result of entrapment of ectodermal layer when the first and second branchial arches fuse in the midline. Plunging dermoid cyst and lateral dermoid cyst are relatively rare entitiy thus posing diagnostic challenge. Whereas, ranula is a pseudocyst, that occurs due to extravasation of salivary secretion into the connective tissues after trauma or infection of the sublingual gland. Treatment approach is different for ranula and dermoid cyst. Ranula can be treated by marsupialization and it has a low level of recurrence, whereas dermoid cyst is treated by surgical excision. Here we present a case of lateral dermoid cyst floor of mouth in a child who had aspiration and marsupialization done before assuming it to be ranula and hence failure of treatment.

Keywords: Dermoid cyst, plunging ranula, developmental anomaly, floor of mouth.

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Sahana. P