Two subtypes

1. Melanoma arising in a pre-existent blue nevus (common or more often cellular) or denritic melanocytosis including nevus of Ota, Ita & pilar neurocristic hamtoma
2. Melanoma in which blue nevus-like features (dendritic cells & melanophages) are seen within a spindled or epithelioid melanoma

Clinical features

•Usually slowly growing tumors

•Predilection for the scalp

•M>F

•No age predilection & exceptionally, lesions can develop in children

•High grade tumor probably related to delay in diagnosis & hence marked tumor thickness

•Metastases develop in around 50% of cases to lymph nodes, lung & liver

Histological features

•Develops within a precursor lesion as one or more nodules of epithelioid or spindled cell melanoma

•Or melanoma showing admixed blue nevus-like features (dendritic cells and melanophages) in the absence of a precursor lesion

•The latter may show a dumbbell appearance at low power or scanning magnification

•Nuclear pleomorphism with prominent nucleoli, mitotic activity & abnormal mitoses

•Necrosis sometimes present

•Occasionally perineural infiltration or vascular invasion seen

•Mutations in DNAQ or GNA11, Mutations in BAP1, SF3B1 & E1F1AX

Melanoma arising in a pliar neurocristic hamartoma