Search

Dermatologists stand at the gateway of individualization of classification, treatment, and outcomes of acral melanoma patients. The acral melanoma genetic landscape differs in vital ways from that of other cutaneous melanomas. These differences have important implications in understanding pathogenesis, treatment, and prognosis. The selection of molecularly targeted therapy must be adapted for acral melanoma. It is also critical to recognize that tumor development is far more complex than an isolated event, reliably treated by a medication acting on a single target. Tumors exhibit intratumor genetic heterogeneity, metastasis may have different genetic or epigenetic features than primary tumors, and tumor resistance may develop because of the activation of alternative genetic pathways. Microenvironmental, immune, and epigenetic events contribute and sustain tumors in complex ways. Treatment strategies with multiple targets are required to effectively disrupt the tumor ecosystem. This review attempts to translate the current molecular understanding of acral melanoma into digestible concepts relevant to the practice of dermatology. The focus is tumor genetics defining potentially treatable cancer pathways, contextualized within the relevant pathologic and molecular features., Graphical abstract

Summary Next generation sequencing (NGS) has unravelled the genetic alterations that underlie the pathogenesis of cancer. It is now becoming integrated into routine clinical diagnostics of malignant tumours. NGS supports diagnosis, identifies therapeutic targets, reveals resistance mechanisms and facilitates disease monitoring. It takes a central function in the implementation of cancer therapies adapted to the molecular alterations of tumours.

Background. The evolution of primary glioblastoma (GBM) is poorly understood. Multifocal GBM (ie, multiple synchronous lesions in one patient) could elucidate GBM development. Methods. We present the first comprehensive study of 12 GBM foci from 6 patients using array-CGH, spectral karyotyping, gene expression arrays, and next-generation sequencing. Results. Multifocal GBMs genetically resemble primary GBMs. Comparing foci from the same patient proved their monoclonal origin. All tumors harbored alterations in the 3 GBM core pathways: RTK/PI3K, p53, and RB regulatory pathways with aberrations of EGFR and CDKN2A/B in all (100%) patients. This unexpected high frequency reflects a distinct genetic signature of multifocal GBMs and might account for their highly malignant and invasive phenotype. Surprisingly, the types of mutations in these genes/pathways were different in tumor foci from the same patients. For example, we found distinct mutations/aberrations in PTEN, TP53, EGFR, and CDKN2A/B, which therefore must have occurred independently and late during tumor development. We also identified chromothripsis as a late event and in tumors with wild-type TP53. Only 2 events were found to be early in all patients: single copy loss of PTEN and TERT promoter point mutations. Conclusions. Multifocal GBMs develop through parallel genetic evolution. The high frequency of alterations in 3 main pathways suggests that these are essential steps in GBM evolution; however, their late occurrence indicates that they are not founder events but rather subclonal drivers. This might account for the marked genetic heterogeneity seen in primary GBM and therefore has important implications for GBM therapy.

Cancer is a collection of complex diseases in which cell proliferation and apoptosis are dysregulated due to the acquisition of genetic changes in cancer cells. These genetic changes, combined with the interrelated physiologic adaptations of neo-angiogenesis, recruitment of stromal support tissues, and suppression of immune recognition, are measurable characteristics in tumor gene expression profiles and biochemical pathways. These measures can lead to identification of disease drivers and, ultimately, can be used to assign therapy. With advances in RNA sequencing technologies, the ability to simultaneously measure all genetic and gene expression changes with a single technology is now possible. The ability to create a comprehensive catalog of genotypic and phenotypic changes in a collection of histologically similar but otherwise distinct tumors should allow for a more precise positioning of existing targeted therapies and identification of new targets for intervention.