BAP1 and nevus: Morphology of this secondary clone strictly depends on the type of second genetic hit: inactivation of the BAP1 (BRCA1-associated protein) gene is the hallmark of BAP1-inactivated nevus (BIN) (33, 34); gain-of-function mutations of CTNNB1 or loss of APC is found in deep penetrating nevus (DPN) (35, 36); loss-of-function of PRKAR1A is typical of pigmented epithelioid melanocytoma (PEM) (37, 38).