Editor,—Choristomas are the commonest limbal tumours in children.1 Four types are recognised—dermoid, dermolipoma, single tissue, and complex choristoma. They arise from metaplastic transformation in the mesoblast lying between the optic nerve and the surface ectoderm. Epithelial and dermal, neural, cartilagenous, smooth muscle, lacrimal, sweat, or sebaceous gland tissue may be present.2-4 They are well circumscribed, white or pale yellow, and may be single or multiple, unilateral, or bilateral5 or form a ring.3 Occasionally, epibulbar choristomata are associated with superficial corneal involvement characterised by a vascularised pannus particularly in those containing lacrimal tissue.6