PSEN1 and melanoma: These data showed that the mean staining intensity for PS-1 was significantly lower in advanced-stage melanoma (0.77 +/− 0.17, N = 20) than in normal skin (2.1 +/− 0.16, N = 10) (p < 0.01) or early-stage melanoma (1.52 +/− 0.21, N = 35) (p < 0.02).