Assessment of clonality in melanocytic nevi

Background: Melanocytic nevi are among the most common lesions in man; howe ver; their pathogenesis remains largely unknown. While often held to be neo plastic, this hypothesis has not been conclusively verified. Alternatively, some authorities have held that melanocytic nevi are hamartomas. More prac tically, difficulty may be encountered in the histologic discrimination of melanocytic nevi from melanoma. It was reported that nevi may be differenti ated form melanoma in females by polymerase chain reaction (PCR) analysis o f loci of human androgen receptor gene on the X-chromosome. However, contra dictory findings have also been reported, suggesting that both acquired nev i and melanoma are clonal. Methods: Fifteen examples of melanocytic nevus were analyzed via PCR for pa ttern of X-chromosome inactivation as indicated by the methylation status o f the human androgen receptor gene. Results: Among 15 nevi analyzed, 11 cases provided informative polymorphism at the androgen receptor loci. Nine of these 11 cases revealed a non-rando m pattern of X-chromosome inactivation. Conclusions: These findings suggest that melanocytic nevi are clonal/neopla stic lesions. As such, they cannot be discriminated from melanoma on the ba sis of clonality.