Comparative genomic characterization of melanoma of known and unknown primary.

BACKGROUND This study aims to genomically characterize melanoma of unknown primary (MUP) in comparison to melanomas of cutaneous primary (MCP). METHODS Eligible cases were collected from the MSK-IMPACT™ Clinical Sequencing Cohort published in the cBioPortal database. Genomic analysis was performed using a hybridization-capture-based next-generation sequencing assay designed to detect mutations, small insertions and deletions, copy number alterations, and genomic rearrangements. RESULTS Among 462 patients of whom 18.4% had MUP, brain metastasis was more common among patients with MUP (23% vs 7.1%). The differences in genomic profiling between MCP and MUP did not reach statistical significance. The 187 MCP and 44 MUP patients treated with immune checkpoint inhibitors had a median overall survival of 49 and 44 months, respectively (p = 0.705). CONCLUSIONS The differences in somatic mutation patterns and survival outcomes were not statistically significant. These findings may allude to similar carcinogenic processes but should be considered exploratory and interpreted with caution.