Dermal dendritic melanocytes and pigmented spindle cells presented no histological evidence of malignancy (CD34−, desmin−, PanCy−, HMB-45+, anti-S-100+, Bcl-2+, MART-1+, focally expression of melan A, 1 % Ki-67+ of the tumour cell nucleoli).
The differentiation of the benign blue nevus (BN) from a malignant blue nevus (MBN) and a malignant melanoma (MM) is still a challenge. Because of the malignant transformation potential of 5.2–6.3 % a histological examination and a conservative surgical approach with close follow up are mandatory.