Whats reason for cystic growth of lacrimal gland?!

Whats reason for cystic growth of lacrimal gland?

in the lateral canthus of eye

Background: Dermoid and epidermoid cysts are examples of choristomas, tumors that originate from aberrant primordial tissue. These tumors contain normal-appearing tissue in an abnormal location. As two suture lines of the skull close during embryonic development, dermal or epidermal elements are pinched off and form cysts, which are adjacent to the suture line. Approximately 50% of these tumors that involve the head are found in or adjacent to the orbit.


Pathophysiology: Orbital dermoid cysts may displace structures in the orbit, especially the globe. If the displacement is great, interference with vision by compression of the optic nerve may result or ocular motility may be disturbed, resulting in diplopia.

Mortality/Morbidity:
Orbital dermoid cysts almost never cause death.
Morbidity is usually of a cosmetic nature; more rarely, proptosis and diplopia may result. A traumatically ruptured dermoid may result in dramatic orbital and periocular inflammation.

Age: These tumors more commonly are noted initially in young children; however, they may appear or grow at any age.

History:
Patients generally complain of a mass, which is visible in the orbital area. Growth of these lesions is generally slow.
In adults, dermoids may become symptomatic for the first time and grow considerably over a year. Based on this fact, some workers conclude that these lesions may be dormant for many years or have intermittent growth.

Physical:
Children: The most common location is in the superior temporal aspect of the orbit. The mass is generally less than 1 cm in diameter, nontender, and oval-shaped.
Usually, little displacement of the globe occurs.
Because it has no attachment to the skin, it can be differentiated from a sebaceous cyst. The cyst usually is tethered to the periosteum of the bone near suture lines, including the sinuses or intracranial cavity.

Adults: The cysts are palpated less easily and have more vague borders. They are more likely to displace the globe, possibly growing or eroding their way into adjacent structures.

Inflammation: If the cyst ruptures, either spontaneously or with trauma, a pronounced inflammatory response will occur that may mimic orbital cellulitis.
The inflammation may be suppressed by corticosteroids, but excision is required to prevent recurrence.

Neurologic findings: Rarely, the cyst may press on the optic nerve and create the typical symptoms of optic nerve compression, as follows: reduced visual acuity, reduced color and brightness perception, and a relative afferent pupillary defect.
More rarely, the cyst may induce diplopia by physically restricting movement of the globe or by compressing cranial nerves III, IV, or VI.

Causes:
No known causes exist.
Other diagnostic considerations
Ruptured dermoid cysts may mimic rhabdomyosarcoma.
Pediatric metastatic cancers
Orbital cellulitis