Targetoid haemosiderotic nevus: four cases and a literature review

Background Targetoid haemosiderotic nevus (THN), a distinct clinical form of melanocytic nevus, is characterized by the sudden development of a purpuric halo surrounding a pre-existing nevus, easily mistaken for melanoma. Objectives To summarise the clinical, dermoscopic and histopathological findings of THN in order to better recognize and manage this condition. Materials & Methods We describe four cases and provide a review of the literature based on a search in PubMed. Overall, the clinical, dermoscopic and pathological findings of 15 THN cases are summarised. Results THN was characterized by a sudden onset of a purpuric halo surrounding a pre-existing nevus without any apparent trigger which occurred mainly in young females. Dermoscopically, the central nevus showed a black-brown, globular or homogeneous pattern, possibly interspersed with reddish, purple, or black structureless areas and comma-shaped vessels. The peripheric purpuric halo had two patterns: one with homogeneous reddish or purplish red areas, and another with an inner pale and outer homogeneous reddish or purplish red zone. The pathological findings showed an intradermal or compound nevus, dilated vessels, and extravasated erythrocytes, possibly accompanied by perivascular inflammatory infiltration and fibrin and hemosiderin deposits. Conclusion THN is a benign lesion that usually requires no intervention other than follow-up observation. Dermoscopy is a useful non-invasive diagnostic tool, and biopsy can be avoided. The purpuric halo resolves spontaneously within two to four weeks with rare recurrence.