Lentigo maligna is a melanoma in situ, that progresses very slowly and can remain in non-invasive form for years. The transition to true melanoma is marked by the appearance of a bumpy surface (itself a marker of vertical growth and invasion), at which point it is called lentigo maligna melanoma. It is normally found in the elderly (peak incidence in the 9th decade), on skin areas with high levels of sun exposure like the face and forearms. Some authors do not consider lentigo maligna to be a melanoma. Incidence of evolution to lentigo maligna melanoma is very low, about 2.2% to 5% in elderly patients. It is also known as "Hutchinson's melanotic freckle".