Melanoma is very heterogeneous in aspect, behavior, genetic bases, risk factors. Sometimes it is extremely difficult to recognize it, even for a specialist. Early detection can be facilitated by the so called "ABCDE rule" (you can easily find it on the web, where are showed useful images too), but it could be not enough. Observe accurately the calendar of follow up by people with high risk factors often makes the difference between death and life. The follow up is not possible for everyone because there are too many people in the world compared to the number of dermatologists. Risk factors: age>50 years, high number of nevi, familiar melanoma (someone in your family has/had melanoma), self history of melanoma, others (e.g. genetic factors). However, everyone should frequently do self skin examination (for example, in a couple each other examination). Be aware: sometimes the thickness of melanoma is not prognostic. Some melanomas increase very fast.Minor risk factors: between non UV extrinsic factors for example there are smoking, coffee, alcohol, others and even some drugs (e.g. Sildenafil, best known as Viagra, promotes cell invasion).There is also a relationship between melanoma and other deseases: childhood cancer, Parkinson's disease, Chronic Lymphocytic Leukemia (CLL), Small Lymphocytic Lymphoma (SLL).