Malignant amelanotic melanoma developing from an intradermal naevus in a patient with oculocutaneous albinism.

A 43-year-old Taiwanese man who had oculocutaneous albinism type 1 presented with a tumorous lesion over the pubic region. Within the tumour, there was a small pinkish plaque. Histopathologically, the tumour revealed benign naevus cells in the upper dermis and atypical malignant tumour cells in the deeper dermis. Immunohistochemistry using HMB-45 showed intensive positive staining in the deeper dermal tumour cells. Amelanotic malignant melanoma (MM) originating from a pre-existing intradermal naevus was diagnosed.