PMEL and nevus: In addition, we examined the expression levels of CCKAR and CCK in pigmented nevus (n = 4; HMB-45 negative and Melan A positive) and blue nevus (n = 3; HMB-45-weakly positive and Melan A positive) and found no positively stained cells in all cases of pigmented nevus and blue nevus, as represented by one case of each nevus (Figure 1a).