Extrachromosomal DNA in cutaneous squamous cell carcinoma is associated with increased nodal disease

Abstract Extrachromosomal DNA (ecDNA) is a mechanism of oncogene amplification that occurs in many cancers and has been linked to worse patient outcomes. While ecDNA has previously been identified in cutaneous melanoma, it has yet to be described in cutaneous squamous cell carcinoma (cSCC). Using whole genome sequencing and transcriptomic data of primary and metastatic cSCC tumors, we establish the presence of ecDNA in cSCC and confirm elevated expression of ecDNA-associated genes. We also find that the presence of ecDNA correlates with a higher lymph node ratio, a measure of disease severity. Together, these findings are the first to report ecDNA in cSCC and suggest that ecDNA gene amplifications promote an aggressive cSCC phenotype.