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].