Epibulbar choristomas containing lacrimal tissue. Clinical distinction from dermoids and histologic evidence of an origin from the palpebral lobe.

Three new cases of epibulbar choristomas, all containing lacrimal tissue, are presented and compared with those reported previously in the literature. The first and second cases were unilateral, complex choristomas, consisting of ectopic lacrimal tissue, smooth muscle, and cartilage; the first case was also remarkable for the presence of lesional tissue in the peripheral cornea and evidence of progressive growth during puberty. The third case was a bilateral, complex choristoma, manifesting epibulbar lacrimal tissue, cartilage, and smooth muscle; also associated were bilateral optic nervehead colobomas and a uniocular focus of posterior scleral cartilage demonstrated by computed tomography (CT) scanning. On clinical examination, all three lesions displayed highly vascularized thickenings of the conjunctiva with diagnostically useful gelatinous elevations, which corresponded microscopically to lobules of lacrimal tissue. In addition, all three cases had the interesting diagnostic feature of superficial corneal scarring or sclerosis, with a fine vascularity adjacent to the conjunctival lesional tissue. Electron microscopy of the third case demonstrated completely normal cytoarchitecture of the lacrimal tissue. Because of the frequent presence of Müller's smooth muscle in epibulbar lacrimal choristomas, the authors propose that these lesions represent embryologic ectopias or overly extensive field effects of the palpebral lobe of the lacrimal gland.