Malignant melanoma, with a scale bar to show the size. This case consists of a pigmented papule on the proximal arm with asymmetry, irregular border and red, brown, and black colour variation. Melanomas are invasive cancers, and may spread to other parts of the body (metastasis). If this occurs, the prognosis is poor. If the cancer has not spread, surgical removal may effect a cure. Melanomas are the most dangerous form of skin cancer.