Phakomatous choristoma may be located in the eyelid or orbit or both.

PURPOSE: Phakomatous choristoma is a rare congenital tumour of lenticular origin. The exact location at clinical presentation is controversial, but herein we provide evidence that phakomatous choristoma may be located in the lower eyelid or orbit or both.
METHODS: Case report of an infant presenting with a mass in the lower eyelid at birth, a systematic review of previous cases of phakomatous choristoma and an outline of the histopathological features in normal mid-facial embryonic development at different gestational ages.
RESULTS: The histopathological features of the present case were consistent with those of a phakomatous choristoma. The preoperative imaging studies and clinical findings at surgery suggested that the tumour occupied parts of both the lower eyelid and anterior orbit. Histopathological sections of a normal human embryo showed that at the 26-mm stage of development the embryonic lens is formed but the bony walls defining the orbit are not yet present.
CONCLUSION: Phakomatous choristoma arises in a setting of undifferentiated mesenchymal tissue which later may develop into the lower eyelid or orbit depending on the choristomatous elements being deposited superficial or deep to the embryonic surface.