Pathology of Halo Nevus - Dr. Sampurna Roy MD

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Pathology of Halo Nevus

A pigmented skin lesion surrounded by depigmented halo and nevus cells in a dense infiltrate of lymphocytes.

Dr Sampurna Roy MD

Dermatopathology Quiz Case: 171

Answer - Halo Nevus

Halo nevus is a type melanocytic nevus which is usually noted in children and young adults.

The lesion may present as single or multiple round or oval shaped, tan brown, uniform central nevi which is surrounded by a amelanotic ring upto several milimeters in width around the melanocytic naevus.

Clinical Differential Diagnosis : Meyerson's Naevus - eczematous halo around the nevus.

Microscopic features:

Histologically, a dense lymphocytic infiltrate is present in the dermis which may obscure the melanocytic component.

Nevus cells are present in nests or singly within the lymphocytic infiltrate.

The number of nevus cells depend on the stage at which the biopsy was taken.

Some cells show cytological atypia. (Differential Diagnosis: In melanoma such a dense diffuse lymphocytic infiltrate is usually not present.)

Some macrophages and factor XIIa-positive dendrocytes may be present in the infiltrate.

In some cases, the melanocytes may be epithelioid in type and may display some cytological atypia.

The lymphocytes are mostly CD8- positive lymphocytes.

These cells express CD69 and tumour necrosis factor-alpha.

Depigmented halo shows an absence of melanin pigment and melanocytes in the basal layer.

Both humoral and cell mediated immunity are involved in the rejection of nevus cells and formation of halo naevus.

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