Can blue nevi become malignant?

Yes. Malignant blue nevi can develop de novo in existing cellular blue nevi, or in a nevus of Ota (see below). Most commonly, the lesion presents as an expanding dermal nodule that may ulcerate. As with other forms of cutaneous melanoma, metastases may develop. Malignant blue nevi are tumors of older individuals. It is more frequent in males then females. The scalp and extremities are the most common sites of occurrence. The prognosis in malignant blue nevi is poor. However, malignant blue nevi are rare, and often there is controversy regarding their histopathologic diagnosis.

Zembowicz A, Mihm MC: Dermal dendritic melanocytic proliferations: an update. Histopathology 45:433–451, 2004.