Basal cell carcinoma (BCC) is the most common cutaneous neoplasia in fair-skinned individuals usually characterized by locally destructive growth and invasion of surrounding tissue. BCC is primarily driven by the aberrant activation of the Sonic Hedgehog pathway (HH), with the majority of BCCs carrying mutations in PTCH1 or SMO genes. However, the great variability in morphology, aggressiveness and response to treatment of BCC remains unexplained and highlights the hypothesis that additional genes might contribute to tumorigenesis of different BCC subtypes. We designed a BCC-specific target panel for next generation sequencing (NGS) using the Ion TorrentTM technology in order to identify additional molecular alterations in cancer-related genes that might contribute to carcinogenesis or histopathologic diversity. Sixty-nine BCCs (35 superficial and 34 nodular) and matched blood samples and/or normal tissue, underwent target sequencing on Ion PGMTM System platform of a cancer panel of 12 genes (CSMD1, CSMD2, DPH3 promoter, PTCH1, SMO, GLI1, NOTCH1, NOTCH2, TP53, ITIH2, DPP10, STEAP4), which was designed by using the Ion Ampliseq technology. Somatic mutations in TERT promoter gene (from position -27 to -286 from ATG start site), were analyzed by direct Sanger sequencing. We confirmed the central role of PTCH1 and TP53 genes that harbored mutations in 72% and 65% of BCCs, respectively. Additionally, we found TERT promoter mutations in 59% of cases, being -146C>T the most frequent one. A high mutation rate was observed also in CSMD1, CSMD2, NOTCH1 and NOTCH2 genes. Our custom-designed NGS approach identified recurrent mutations within both established and unknown BCC-related genes. These findings offer new insight and improved understanding of the pathogenesis of BCC.

Next-generation target sequencing analysis identifies multiple somatic mutations in basal cell carcinoma.