CELF1 and metastatic melanoma: Moreover, a retrospective series of benign nevi (n = 47) and clinically annotated primary and metastatic melanoma biopsies (n = 138) confirmed a significant accumulation of CELF1 in malignant lesions, particularly in vertical growth phase cutaneous melanomas (two-tailed Student’s t test p < 0.005; Fig. 1f, g; see scoring system in Supplementary Fig. 5c).