Evaluation Of Genetic Heterogeneity In Paired Lymph Node Metastases From Melanoma Patients Using Next-Generation Sequencing (Ngs) Approaches

9048 Background: In our previous experience (JCO 2012;30:2522-9), we demonstrated a high consistency of BRAF and NRAS mutations between primary tumors and lymph node metastases in melanoma patients. A subset of paired samples of multiple asynchronous lymph node metastases from that series was here screened mainly using NGS technologies in order to better elucidate the existence of a real genetic homogeneity during clonal expansion to lymph node sites. Methods: Genomic DNA was isolated from frozen tissues of paired asynchronous lymph nodes, ascertained for presence of melanoma metastases (at least 80% of metastatic cells), using standard methods. Specimens from 12 patients were analyzed for mutations in 50 most common cancer genes with the Ion Torrent AmpliSeq Cancer Panel HotSpot.V2 (CHPv2) on the Ion PGM sequencer. All variants detected by NGS were confirmed through PCR-based Sanger sequencing. Paraffin-embedded tumor tissues from the same series were evaluated by fluorescence in situ hybridization (FISH...