A pigmented scalp nodule: malignant blue nevus.

The malignant blue nevus is an aggressive dermal melanocytic neoplasm. The lesion occurs most frequently on the scalp of men in their fifth decade of life, often metastasizes to the regional lymph nodes, and commonly results in fatality. Controversy exists as to whether this lesion is a malignant melanoma in the dermis or a separate neoplasm arising in the architecture of a cellular blue nevus. The lesion is treated with wide local excision and close monitoring for the occurrence of metastatic disease.