Epidermal inclusion cysts are developmental anomalies. The most common theory for their appearance in the midline sublingual area is that the cyst develops from entrapped ectodermal tissue of the first (mandibular) and second (hyoid) branchial arches, which fuse during the third and fourth weeks in utero. A second theory suggests that traumatic implantation from a surgical or accidental injury forces epithelial cells into the deeper tissues.1