Respiratory epithelium in a cystic choristoma of the limbus. A female newborn had a cystic, whitish gray mass at the inferotemporal limbus of the left eye. At age 3 weeks, the newborn underwent excision of the tumor, corneal patch grafting, and superior sector optical iridectomy. Histopathologic and electron microscopic examination of the excised tissue revealed a choristoma consisting of cysts lined with respiratory epithelium. To our knowledge, respiratory epithelium in a limbal choristoma has not been previously reported. 