Comprehensive analysis of 112 melanocytic skin lesions demonstrates microsatellite instability in melanomas and dysplastic nevi, but not in benign nevi

Introduction: Alterations in the length of DNA repetitive sequences (microsatellite instability (MSI)) represent distinct tumorigenic pathways associated with several familial and sporadic tumors. Material and methods: To investigate the prevalence and frequency of MSI in melanocytic lesions, the polymerase chain reaction (PCR)‐based microsatellite assay was used to examine formalin‐fixed, paraffin‐embedded tissues of 30 benign melanocytic nevi, 60 melanocytic dysplastic nevi (MDN), and 22 primary vertical growth phase cutaneous malignant melanomas (CMM). Twenty‐four microsatellite markers at the 1p, 2p, 3p, 4q and 9p chromosomal regions were used. Results: MSI was found at 1p and 9p in MDN and CMM but not in benign melanocytic nevi. The overall prevalence of MSI was17/60 (28%) in MDN and 7/22 (31%) in CMM. The frequency of MSI ranged from 2/24 (9%) to 4/24 (17%) and was most commonly found at D9S162. There was a statistically significant correlation between degree of atypia and frequency of MSI (p