Introduction
Epidermoid, dermoid, and teratoid cysts are nonodontogenic lesions derived from the germinative epithelium [1]. These cysts can be found anywhere in the body, particularly in areas where embryonic elements fuse together [2,3]. Most of the reported cases have been localized in the ovaries, the testicles, as well as the hands and feet [2,3]. The incidence in the head and neck has been reported to be about 7% [4], with only 1.6% of cases presenting in the oral cavity [5]. The diagnosis of epidermoid cyst remains a great challenge for clinicians; as the clinical aspect is not specific and may mimick many other disease or condition. Therefore, several investigations as ultrasonography, fine needle aspiration, MRI are recommended to rule out other diagnosis [6].
The definitive diagnosis of epidermoid cyst is based on the anatomopathological exam. These cystic lesions were classified since 1955 by Meyer into epidermoid, dermoid, and teratoid variant. Dermoid cysts are lined by epidermis and contain skin adnexa such as sebaceous glands, sweat glands and hair follicles. When there are no adnexa, these cysts are termed as epidermoid or epidermal with the lining containing only epithelium. Teratoid cysts consist of dermoid material plus tissue of other embryonal sources like respiratory, gastrointestinal and connective tissues such as bundles of striated muscle and distinct areas of fat [2,3].
The epidermoid type is the most common one, comprising 85-90% of all excised cysts [7,8]. The midline or sublingual region of the mouth floor is the most commonly affected area contrary to the buccal mucosa which seems to be an unusual site of occurence [8].