Genetic concordance in melanoma: insights from primary tumors and their matched distant metastases

Melanoma metastasis poses a significant challenge due to its aggressive nature and increasing incidence. Confirming the clonal relationship between the primary melanoma and its metastasis is essential to developing reliable prediction models. Here, we compared the genetic profile of primary melanoma and matched metastasis to assess their genetic clonal relationship. Using a targeted sequencing panel encompassing 330 amplicons, we targeted hotspot regions in 41 cancer genes and 154 single nucleotide polymorphisms. The clonal relation between primary and matched metastasis tumors was evaluated by comparing the mutational status and the copy number variations profile in 15 patients with primarily thin melanomas and distant metastases, or with a long latency between the primary melanoma and distant metastasis. Our findings revealed that only about 50% of the analyzed matched primaries and metastases were clonally or likely clonally related, while the remaining sets were either not clonally related or difficult to determine with certainty the clonal relatedness. The findings of our study illustrate the intricate clonal relationships between primary melanoma and metastasis and raise doubts if the metastatic potential is overestimated in the primary tumors. Further investigation with larger cohorts is needed to better understand this complexity of melanoma metastasis and clonality phenomenon, which should be carefully considered when using primary tumor molecular profiles for prognostic model building or therapeutic guidance in metastatic cases.