MKI67 and melanoma: The cellular blue nevus can infiltrate deep tissue and even reach the spinal cord parenchyma, not really metastasis, but the likelihood of recurrence or malignancy may increase.[4] Different from common pigmented nevus, cellular blue nevus can express HMB45, which is similar to malignant melanoma, but the ki67 index is very low, which is one of the key points for differentiation between cellular blue nevus and malignant melanoma.[10]