The picture shows a divided melanocytic naevus along the margins of the upper and lower eyelid of a teenage boy. He was referred because of two congenital pigmented naevi located opposite to each other, laterally on the right eyelids. During his childhood and adolescent years, they had gradually grown larger and caused cosmetic problems, discomfort with foreign body sensation, and stickiness of the eyelids. The naevi were therefore removed surgically under general anaesthesia by means of a full-thickness pentagonal excision of both the upper and the lower eyelid. A histological examination disclosed a compound naevus with regular naevus cells without atypical features. Follow-up four months later revealed a good cosmetic result and normal eyelid function.
Congenital, divided naevus on the eyelids is a rare condition known variously as kissing naevus, split naevus or divided naevus. The term ‘kissing naevus’ refers to the fact that the two naevi are in contact when the eye is closed. In addition to the cosmetic consequences, such congenital naevi can lead to impaired eyelid function, epiphora and amblyopia (1, 2). The risk of melanoma development is regarded as low (2, 3).
The condition is particularly interesting from an embryological point of view. The eyelids are formed early in fetal development, and at the beginning of the third fetal month they fuse and cover the eye. In the following weeks, melanoblasts migrate from the neural crest out to the epidermis, where they differentiate into melanocytes. After the sixth fetal month, the fused eyelids separate to form an upper and a lower eyelid (1, 2). In this way, a congenital melanocytic eyelid naevus can divide into two and develop its characteristic appearance.