Atypical Histologic Features Associated with Metastasis in Blue Naevi

Atypical blue naevus is a controversial entity with histologic features that can be similar to both benign blue naevi and melanoma.Evaluated were 30 blue naevi for atypical histologic features that conventionally include increased lesion size, increased cellularity, polymorphous spindle and epithelioid cells, vesicular nuclei and prominent nucleoli, intense pigmentation, and infiltrative growth with 'dumbell'-shaped nesting.It was found that when present together, atypical histologic features of fatty infiltration, polymorphous population of spindle and epithelioid cells with prominent nucleoli, perineural infiltration and deep 'dumbell-shaped' lesional cell nesting were associated with sentinel lymph node metastasis.In select cases, these histologic features, when present together, may impart higher clinical risk and may warrant adequate complete lesional excision and sentinel lymph node sampling.