Cellular blue nevus (CBN) lymph node metastases of the neck with no primary skin lesion: a case report and review of literature.

A case of cervical lymph node infiltration by a benign cellular blue nevus (CBN) and a 27-year disease history is presented. 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.