Dermoid and epidermoid cysts represent congenital cystic benign tumours and belong to choroistomas

Dermoid and epidermoid cysts represent congenital cystic benign tumours and belong to choroistomas which originate from aber­ rant primordial tissue. Choristomas are benign tumours that are formed during the embryonic development from the tissues we do not normally expect to be there. Practically, it is normal tissue that is found at the wrong place. During such an embryonic development and formation of the embryonic skull and orbit suture, dermal or epidermal elements remain compressed and form cystic formations with a constant tendency to enlarge and progress [1, 2]. About 50% of these tumours localized in the head appear in the orbit or in its vicinity. Nearly 10% of dermoid head and neck cysts are local­ ized in the orbit, and in this case dermoid and epidermoid cysts of the orbital and periorbital region can be present at different places, which depend on the position of suture, size and degree of growth. More than half of these lesions are localized in the upper­orbital quadrant [3, 4]. Cystic changes are usually discovered early, at birth, but can also be found or even indicate the possibility of growth at any time. The change is usually 1­2 cm in size, soft upon palpation, of an oval shape and mobile under the skin. The inner part of a cyst, which is not accessible to palpa­ ble examination, is usually attached to the bone periosteum near the suture lines. The cyst can very easily be felt in children, while adults have unclear lines and during its growth, the pressure on the bulbus and surrounding bony structures can appear [5, 6, 7]. Clinically, dermoid and epidermoid cysts are divided into superficial (simple) and deep (complicated) cysts. Because of their super­ ficial localization, superficial (simple) cysts rarely develop complications regarding growth and therefore are easily handled surgically. However, they are frequently exposed to inju­ ries and ruptures [8, 9, 10]. Deep orbital dermoid and epidermoid cysts are described as a slow growing mass which spreads during the lifetime. They can form through any bony suture of the orbit, including the upper wall of the orbit. A careful examination is necessary in order to separate superficial from deep lesion formations, because deep lesions can break through the wall of the orbit and propa­ gate into the temporal cavity and sinuses or even into the intracranial area [11, 12]. Differentiation between dermoid and epider­ moid cysts is not usually possible to determine during a clinical examination. A pathohistolog­ ical result shows the difference between these two entities; the basic difference here is the fact that dermoid cysts have sqamous epithelium that SUMMARy Introduction Dermoid and epidermoid cysts of the orbit belong to choristomas, tumours that origi­ nate from the aberrant primordial tissue. Clinically, they manifest as cystic movable formations mostly localized in the upper temporal quadrant of the orbit. They are described as both superficial and deep formations with most frequently slow intermittent growth. Apart from aesthetic effects, during their growth, dermoid and epidermoid cysts can cause disturbances in the eye motility, and in rare cases, also an optical nerve compression syndrome. Case Outline In this paper, we described a child with a congenital orbital dermoid cyst localized in the upper­nasal quadrant that was showing signs of a gradual enlargement and progression. The computerized tomography revealed a cyst of 1.5­2.0 cm in size. At the Maxillofacial Surgery Hospital in Niš, the dermoid cyst was extirpated in toto after orbitotomy performed by superciliary approach. Postoperative course was uneventful, without inflammation signs, and after two weeks excellent func­ tional and aesthetic effects were achieved. Conclusion Before the decision to treat the dermoid and epidermoid cysts operatively, a detailed diag­ nostic procedure was necessary to be done in order to locate the cyst precisely and determine its size and possible propagation into the surrounding periorbital structures. Apart from cosmetic indications, operative procedures are recommended in the case of cysts with constant progressions, which cause the pressure to the eye lobe, lead to motility disturbances and indirectly compress the optical nerve and branches of the cranial nerves III, IV and VI.