Freckle-like nevus (or nigra) is a flat or slightly elevated pigmented lesion with well-defined boundaries. Unlike freckles, they do not fade in winter. There are many different kinds of freckle-like nevi, such as simple freckle-like nevus, solar freckle-like nevus, ink dot-like freckle-like nevus, pancystic freckle-like nevus, clustered freckle-like nevus, mucosal nigra; central facial freckle-like nevus disease; freckle-like nevus syndrome; PUVA-related freckle-like nevus; sunbed-related freckle-like nevus; radiation therapy-related freckle-like nevus; and pattern freckle-like nevus. I. Who is prone to get freckle-like nevus? Men and women, all ages and different races can have freckle-like nevus. People with fair complexion are more likely to get solar freckle-like nevus. Freckle-like nevus syndrome often appears at birth or during childhood. What are the causes of freckle-like nevus? 1.Common causes are ultraviolet radiation: sun damage including sunburn; indoor sunburn; phototherapy, especially PUVA (photochemotherapy). 2.Ion irradiation, such as radiotherapy, can also cause freckle-like nevus. 3. Some familial pancytopenia syndromes may be related to mutations in Ras-MAP kinase, mTOR signaling, and PTEN pathway. What are the clinical features of freckle-like nevus? Freckle-like nevus is divided into different types according to different appearance, location, cause of occurrence, and whether it is related to other diseases. Freckle-like nevus can be single or multiple, and the diameter is usually less than 5 mm. How to diagnose freckle-like nevus? Freckle-like nevus is usually diagnosed based on the typical clinical appearance. If one is unsure or suspects melanoma, one can resort to: dermoscopy; excisional biopsy. Histopathological manifestations are as follows: epidermal thickening; increased melanocytes in the basal layer of epidermis; unlike junctional nevi, there are no melanocyte nests; increased melanin granules in keratin-forming cells; other features vary according to different types of freckle-like nevi; in contrast, freckles are mainly sunlight-induced increased melanin in keratin-forming cells without an increase in the number of melanocytes. V. How to treat freckle-like nevus? Most of them do not need treatment. The following methods can lighten the color of freckle-like nevus: sunscreen with SPF>50; hydroquinone cream; alpha hydroxy acid; vitamin C; retinoic acid; azelaic acid; chemical peeling. Permanent removal methods include: freezing, intense pulsed light, laser.