Epidermoid inclusion cysts are rare in the oral cavity, accounting for less than 0.01% of cysts found there. These cysts are defined as epidermoid if they contain only epithelial lining, dermoid if skin appendages, and teratoid if they contain other tissues such as muscle, cartilage, and bone. This case report describes a case of a plunging ranula that was later diagnosed as an epidermoid inclusion cyst. The patient is a 22-year-old male who presented with swelling in the floor of the mouth and difficulty eating solid foods for the past 4 months. Upon examination, a shiny, pink-colored mass measuring 1 cm × 5 cm was observed, which displaced the tongue upward and backward. MRI scan of the brain, face, and neck revealed a well-defined, non-enhancing cystic mass measuring 6.6 cm × 4.5 cm that extended beyond the sublingual area. Histopathological examination after surgical removal of the cyst revealed that the cyst wall was lined with stratified squamous keratinized epithelium with a retained granular layer, and the cavity was filled with lamellated keratin flakes. The patient recovered well after surgery; no recurrence was observed at the 6-month follow-up.
Keywords: follow-up after cyst removal; oral cavity swelling; plunging ranula; sublingual epidermoid cyst; surgical excision.