Phakomatous Choristoma of the Eyelid and Orbit: A Case Report.

Phakomatous choristoma was first described as a distinct pathologic entity by Zimmerman in 1971. Report of only 26 cases of this tumor so far is an indicator of the rarity of phakomatous choristoma. We present a 4-month-old infant with an orbital mass beneath the right lower eyelid. Surgical excision was undertaken and the histopathologic findings of a dense fibrocollagenous stroma containing small to medium size islands and glandular-like structures surrounded by thick basement membrane and filled by amorphous eosinophilic material confirmed the diagnosis. Immunohistochemical study showed positive staining for S-100 and vimentin and negative staining for cytokeratins, glial fibrillary acidic protein, smooth muscle actin, synaptophysin, CD34, melan-A, and epithelial membrane antigen markers. This is the first patient with phakomatous choristoma presented from our country and the 27th reported case worldwide. Phakomatous choristoma is a rare, benign congenital tumor of lenticular anlage, almost always presenting in the medial lower eyelid and anterior orbit. Surgical excision is curative and allows precise diagnosis due to the unique histopathologic and immunostaining characteristics of this choristoma.