According to a new study, some of the most deadly skin cancers may start in stem cells that lend color to hair, and originate in hair follicles rather than in skin layers. Hair follicles are where immature pigment-making cells develop cancer-causing genetic changes – and in a second step – are exposed to normal hair growth signals, say the study authors. Past models of the disease had argued that sunlight (e.g., ultraviolet radiation) was a major risk factor for melanoma – but current work ar...