Congenital epidermoid cyst results in muscle fusion defect in the upper lip.

Epidermoid cysts are rarely detected malformations in the oral cavity. Their development sites are the sublingual, submaxillary, and submandibular spaces. In this paper, we report a three-month-old infant who was admitted to our hospital due upper lip swelling. Magnetic resonance imaging showed that she had a two-centimeter cystic lesion and fusion defects of orbicularis oris muscle. The cyst was surgically removed and histopathological diagnosis was "epidermoid cyst." In recent literature, we could not find reports related to orbicularis oris muscle fusion defects because of epidermoid cyst.