Halo congenital naevus in a middle-aged patient with vitiligo.

A case of halo congenital naevus is reported on the chest of a 56-year-old Asian woman with pre-existing vitiligo. The naevus measured 3.5 cm x 2 cm and underwent depigmentation around its periphery. Dermoscopic examination showed coarse pigment in the darker centre of the naevus and depigmentation in the surrounding halo. Light microscopy showed well-formed naevus cell nests with coarse melanin granules in the papillary dermis, and surrounding fibrosis. Melanocytes extended into reticular dermis, consistent with a congenital growth pattern. There was no evidence of malignancy. The epidermis was of normal appearance. S100 staining highlighted melanocytes in the dermis. Basal melanocytes were retained at the periphery of the naevus. Based on the clinical history and histological findings, a diagnosis of halo congenital naevus was made. The naevus was not excised.