KIT and mastocytosis: In 2007, the European Union/US consensus group established criteria for cutaneous involvement in patients with mastocytosis, including the presence of typical skin lesions with a positive Darier’s sign (major criterion) and one or two of the following minor criteria: histologically confirmed infiltration of MCs in the dermis (around 40 MCs/mm2) and activating KIT mutations at codon 816 in lesional skin [38].