Figure 1.

Early during embryogenesis, mosaicism can develop through fixation of acquired mutations in cancer susceptibility genes (CSGs). Pareja et al. report evidence of this phenomenon occurring as early as the first cell division. In mature organisms mosaic tissues can develop tumors that are driven by the selective advantage of cells carrying mutations in CSGs, and typically tumors have an increased presence of mutant cells than healthy tissue, consistent with their clonal origins. Blood and tumor tissue were sequenced to identify individuals that developed cancer as a result of mutant CSG mosaicism and used to characterize the cancer development driven by mutant CSG mosaicism and model the developmental timing of the original mutation. This figure was created with Biorender.