Halo nevi are common benign skin lesions that represent melanocytic nevi in which an inflammatory infiltrate develops, resulting in a zone of depigmentation surrounding the nevus. Although Sutton originally described the lesion in 1916 as leukoderma acquisita centrifugum, the lesions were noted earlier, as evidenced by their depiction in the painting The Temptation of Saint Anthony by Matthias Grünwald circa 1512-1516.[1]
Because melanoma that has undergone regression may appear gray or white, halo nevi have been erroneously confused with melanoma and have been the source of much anxiety among both clinicians and patients. Nevertheless, they are entirely benign lesions and of only cosmetic significance.
The etiology is unknown, but halo nevus is believed to be due to an immune response against melanocytes. Numerous studies have attempted to unravel the immunologic mechanisms by which an immune response develops to existing aggregates of nevus cells.[2] The infiltrating cells are predominantly T-lymphocytes, and cytotoxic (CD8) lymphocytes outnumber helper (CD4) lymphocytes by a ratio of approximately 4:1. These, as well as scattered macrophages, comprise most inflammatory cells in halo nevi.[3] As seen in vitiligo, melanocytes in the epidermis in the halo component of the nevus are completely absent, suggesting a similar etiologic mechanism.[4] A distinct relationship seems exist that distinguishes halo nevus in patients without vitiligo and halo nevus in patients with vitiligo, although definitive features have not been determined. Multiple halo nevi, the presence of Koebner phenomenon, and a family history of vitiligo have been identified as possibly increasing the risk of vitiligo in patients with halo nevi.[5] The exact role that the lymphocytes play in the regression of halo nevi has not been fully determined, although a theory of direct cytotoxic effects on melanocytes seems plausible.
Of interest, circulating antibodies to the cytoplasm of melanoma cells have been detected in patients with halo nevi.[6] Because these antibodies have disappeared after removal of the halo nevus, they were thought to be related. Subsequent investigation failed to reveal a temporal relation between the appearance of these antibodies and the regression of nevus cells, and these antibodies are now believed to appear as a consequence of the release of cytoplasmic proteins of halo nevus melanocytes secondary to cell damage.
Ultrastructurally, advanced lesions of halo nevus show dermal macrophages containing portions of nevus cells. While it is clear that an immunologic mechanism results in the demise of melanocytes in halo nevi, the precipitating cause and the exact role of the lymphocytes remain unknown.[7]
The incidence of halo nevi in the population is estimated to be 1%.[8] Patients with Turner syndrome have been reported to have an increased incidence of halo nevi.[9]
Race
All races are susceptible to the development of these lesions. A familial tendency for halo nevi has been reported.
Sex
No sexual predilection is reported.
Age
Halo nevi are found most commonly in children.[10] The average age of onset is 15 years.
Patients should be instructed to monitor the lesion. If changes occur that suggest irregularity or if such symptoms as bleeding, itching, pain, or ulceration develop, the patient should be reevaluated promptly to exclude the possibility of cutaneous melanoma. For patient education resources, see the patient education article Mole Removal.
Patients with halo nevi are usually asymptomatic. The central nevus may or may not involute with time. Repigmentation often takes place over months or years; however, it does not always occur. Occasionally, inflammation occurs with crusting in the depigmented zone of a halo nevus. Most commonly, the chief complaint is that of a changing mole (or moles).
Halo nevi are usually single but may be multiple. They can develop anywhere on the body but are seen most frequently on the trunk. Clinically, they appear as one or more uniformly colored, evenly shaped, round or oval nevi centrally with even peripheral margins of hypopigmentation. The central nevus may be tan, pink, or brown. The width of the halo is variable but is generally of uniform radial distance from the central nevus.
View Image
Classic appearance of a halo nevus.
View Image
Note the central pink papule (intradermal nevus) and the surrounding halo. The halo is of uniform width at all points, and no inflammatory component c....
Lesions that are not uniform in shape and color or that have a papular component that is not centrally located should be considered for biopsy to exclude the presence of melanocytic atypia.
The histology of halo nevus is variable depending on the age of the lesion; however, in most cases, a dense, somewhat bandlike lymphocytic infiltrate is present in the papillary and often reticular dermis with nests of nevus cells located centrally. The lesion usually demonstrates a dome-shaped architecture similar to that seen in noninflamed nevi. Identifying residual nevus cells may be difficult in some cases, particularly with older lesions or those in which the infiltrate is quite dense. Mitotic figures usually are not seen, although occasional apoptotic cells may be identified. Macrophages may be seen within the infiltrate, some of which are laden with melanin, although, surprisingly, the number of melanophages is less than would be expected in an inflamed melanocytic lesion.
View Image
At low magnification, a dome-shaped papular lesion reveals a dense infiltrate of lymphocytes in the dermis (hematoxylin and eosin, original magnificat....
View Image
Higher magnification reveals nests of nevus cells with numerous lymphocytes surrounding them and in the interstitium (hematoxylin and eosin, original ....
In more mature lesions, nevus cells may appear to be absent or decreased in number. Clinically, a noninflammatory halo nevus may demonstrate a halo, but, histologically, virtually no inflammatory infiltrate may be present. Conversely, some nevi may demonstrate marked inflammation, but, clinically, no halo is visible. Therefore, clinical correlation is important in rendering a diagnosis of halo nevus. The most important lesion to differentiate from halo nevus is melanoma (see Table).
Table. Distinguishing Features of Halo Nevus and Melanoma
The chief diagnostic consideration in patients with halo nevi is melanoma that is undergoing regression, although making this distinction is not usually difficult. Primary melanoma is usually solitary, whereas halo nevi are commonly multiple. Furthermore, children are affected more commonly with halo nevi; adults are affected far more commonly by melanoma. Nevertheless, the risk of an individual lesion should be assessed based on both its history and clinical features as a whole. Any characteristic deemed suspicious for possible malignant behavior should be definitively addressed.[12]
Melanomas with surrounding white or hypopigmented zones usually have been present for an extended period of time, and the white areas represent zones of regression. Thus, the "halo" of a regressing melanoma is irregular in shape and variable in radial width, as opposed to the evenly distributed, circular zone of hypopigmentation in true halo nevi, which is distributed around the central nevus. Furthermore, melanomas usually exhibit the characteristic clinical signs of breadth, asymmetry, poor circumscription, and color irregularity with black foci that usually allow the diagnosis to be rendered with relative ease.
In spite of clinically benign features, the presence of a new "halo nevus" in an older adult should be regarded with a high index of suspicion for melanoma and may warrant performing a biopsy. In those patients where a potential malignancy is in question, a dermatologist should be consulted.
The course of halo nevi is normally uncomplicated. Problems arise in those instances where the lesions have been misdiagnosed or when the lesion is excised and wound complications develop postoperatively.
Edward J Zabawski, Jr, DO, Medical and Surgical Dermatology
Disclosure: Nothing to disclose.
Coauthor(s)
Clay J Cockerell, MD, President and Owner, Cockerell Dermatopathology; Adjunct Clinical Professor, Department of Internal Medicine (Dermatology), Division of Dermatopathology, University of North Texas Health Science Center at Forth Worth
Disclosure: Nothing to disclose.
Specialty Editors
Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Disclosure: Nothing to disclose.
Chief Editor
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Susan M Swetter, MD, Director, Pigmented Lesion and Melanoma Program, Professor, Department of Dermatology, Stanford University Medical Center and Cancer Institute, Veterans Affairs Palo Alto Health Care System
Note the central pink papule (intradermal nevus) and the surrounding halo. The halo is of uniform width at all points, and no inflammatory component can be seen. Note the normal nevus directly inferior.
At low magnification, a dome-shaped papular lesion reveals a dense infiltrate of lymphocytes in the dermis (hematoxylin and eosin, original magnification X40).
Higher magnification reveals nests of nevus cells with numerous lymphocytes surrounding them and in the interstitium (hematoxylin and eosin, original magnification X40).
Classic appearance of a halo nevus.
Note the central pink papule (intradermal nevus) and the surrounding halo. The halo is of uniform width at all points, and no inflammatory component can be seen. Note the normal nevus directly inferior.
At low magnification, a dome-shaped papular lesion reveals a dense infiltrate of lymphocytes in the dermis (hematoxylin and eosin, original magnification X40).
Higher magnification reveals nests of nevus cells with numerous lymphocytes surrounding them and in the interstitium (hematoxylin and eosin, original magnification X40).
Halo Nevus
Melanoma
Nevus cells in nests
Single atypical melanocytes at all levels of the epidermis and aggregates of atypical melanocytes in the dermis
Lesion symmetrical
Lesion asymmetrical
Maturation of nevus cells
Lack of maturation
Mitotic figures rare or absent
Mitotic figures present
Lymphocytic infiltrate present diffusely throughout lesion
Lymphocytic infiltrate tends to be at be concentrated at periphery
){kind=link}
){kind=link}
){kind=link}
){kind=link}