M 15, back
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Halo nevus is a common melanocytic nevus with a chronic inflammatory infiltrate resulting in a zone of depigmentation surrounding the nevus.
The infiltrating cells are predominantly T-lymphocytes, and cytotoxic (CD8) lymphocytes outnumber helper (CD4) lymphocytes.
Occurs most commonly in children (average age of onset is 15 years).
Histology of halo nevus varies depending on the age of the lesion; a dense, somewhat bandlike lymphocytic infiltrate is present in the papillary and reticular dermis with nests of nevus cells located centrally.
The lesion is dome-shaped architecture similar to other dermal or compound nevi.
Identifying residual nevus cells may be difficult in some cases.
S-100 stains the nevus cells.