Mutation hotspots in such genes as FGFR3, TERT, PLEKHS1, and GPR26, frequently mutated in UTUCs [55,67,68], or the coding regions of such genes as PTEN and PIK3CA, frequently mutated in EC [69,70], could also be incorporated into the multiplex to identify MSS tumours that, although in the minority, do occur within LS patients. This evidence concerns the gene PIK3CA and neoplasm.