[Genetic changes and biological potential of proliferative nodule in congenital pigmented nevus]

Objective: To study the genetic changes and biological potential of proliferative nodule in congenital melanocytic nevus. Methods: Whole-exome sequencing was carried out using the technique of next-generation sequencing (NGS) in order to detect the genomic alterations of two cases of proliferative nodules (PN) in congenital melanocytic nevi (CMN). Twelve cases of CMN and ten cases of malignant melanoma were used as benign and malignant controls, respectively. Mutated genes that possessed statistically significant difference between benign and malignant controls were listed, according to what benign and malignant statuses were classified and clustered. The heatmaps of clustering analyses were depicted using heatmap package. Fluorescence in situ hybridization (FISH) was also used to validate the above results. Results: Eighty-six common somatic gene mutations were detected in two samples of PN. Compared with CMN, PN had 52 more mutated genes. Furthermore, 22 of these 52 mutated genes were also detected in malignant melanoma samples. Two cases of PN fell between benign CMN and malignant melanoma in germline mutation clustering. Both cases of PN were positive in the FISH tests. Conclusions: The genetic changes of PN partially overlap with those of CMN and malignant melanoma. Therefore, although most of the PN manifest as a benign lesion clinically, it may have certain malignant potential at the genetic level, and warrant long-term monitoring and follow-up.