Halo Nevi

 May be absent in late stage (regressed) lesions



• Melanocytic markers may be useful to confirm presence of melanocytes

• Spitzoid features may be present in some cases (halo Spitz nevi)

• Reactive atypia may be seen

• Dermal component should show evidence of maturation with descent

• Mitoses should be rare to absent




Ancillary Tests




• Melanocytic markers may be useful to confirm presence of melanocytes
image S100, SOX10, Melan-A, HMB-45, p16


Top Differential Diagnoses




• Melanoma
image Can show associated inflammatory infiltrate but usually milder than halo nevi

image Lack of symmetry and circumscription

image Pagetoid scatter and dermal mitoses may be present

• Myerson nevus (eczematous nevus)

image
Clinical Photograph of Halo Nevi
Two halo nevi seen on the back of a young adult are oval, well demarcated, and depigmented (skin colored or paler). With time, the white area may replace the nevus entirely image.


image
Halo Nevus Showing Dense, Band-Like Inflammatory Infiltrate
Halo nevus is characterized by a dense, band-like lymphohistiocytic infiltrate in the dermis image. Several junctional and superficial nests of melanocytes image can be appreciated upon close inspection.

image
Halo Nevus at Higher Magnification
Higher magnification shows a dense lymphohistiocytic infiltrate with scattered melanophages image. The melanocytes are mildly enlarged and atypical appearing image but show no mitotic activity.

image
Melan-A Immunohistochemistry in Halo Nevus
Melan-A immunohistochemistry in a halo nevus strongly highlights the residual junctional and dermal cells. S100 and Melan-A are usually diffusely positive, whereas HMB-45 usually only highlights the junctional cells (which can be useful in the differential with melanoma).


TERMINOLOGY


Synonyms




• Sutton nevus

• Nevus depigmentosa centrifugum


Definitions




• Nevus with clinically depigmented halo surrounding pigmented area
• Dense inflammatory infiltrate typically present

image Histologically heavily inflamed nevi that lack clinical halo may be said to show halo reaction/phenomenon, but they are not true halo nevi


ETIOLOGY/PATHOGENESIS


Inflammatory Process




• Thought to be reaction to melanocytic antigens

• Infiltrate includes numerous T cells, including cytotoxic CD8(+) cells that may induce melanocyte apoptosis


CLINICAL ISSUES


Epidemiology




• Age
image Usually young patients (children and young adults)

image Patients over 40 years old uncommon

– Should raise concern for possibility of melanoma at another site

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Halo Nevi
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