People who answer with 'are you really that stupid' are ignorant. They tend to take information at face value without critical consideration of the amount of information required to definitively answer such a question. It is assumed that skin cancers need to be treated (surgically and/or medically), otherwise they’ll eventually become dangerous. If you had a suspicious bump that’s no longer there, however, there’s no way to tell whether or not it was cancer. Many have claimed that a simple regimen (e.g. applying frankincense or juicing) helped them destroy a tumor. If even one of these claims is true, it may indicate that it’s possible to destroy a tumor without knowing it (perhaps your new moisturizer has the 'magic' ingredient!). There are stories about people who, when they went in to get their tumor surgically removed, were told (by a baffled oncologist) it was nowhere to be found. Also, some research has shown a correlation between emotional states and cancer growth/shrinkage. Thus, until cancer in all its various manifestations is understood completely (unlikely to happen soon), nobody can say with absolute confidence that a tumor cannot disappear on its own.