MODEL RELEASED. Lentigo maligna melanoma on the skin of the arm of a 90-year-old woman. Melanoma is a form of skin cancer that arises from melanocytes, the cells that produce melanin, the pigment that gives skin its colour. Lentigo maligna melanoma is a melanoma that has evolved from a lentigo maligna, a non-invasive form of melanoma. The main cause of melanoma is exposure to ultraviolet (UV) radiation in sunlight. It is an aggressive cancer that often spreads (metastasizes) to other parts of the body. Treatment is with surgical excision of the melanoma.