Melanoma of unknown primary: New perspectives for an old story

Melanoma of unknown primary site (MUP) comprises 3–4 % of all melanomas. It mostly presents in lymph nodes (LNs), followed by subcutaneous sites, and visceral organs; nevertheless, there is a trend of increase in the relative incidence of visceral counterpart in recent years. Spontaneous regression of the primary lesion is a well-established theory, based on the evidence that melanoma can undergo regression at the primary site.