KRAS and lymphoma: Similarly, sporadic activation of K-ras (due to the RosaCreERT2 allele producing low levels of background recombination in the absence of the inducer 21) resulted in decreased survival of untreated K-ras mice (Figure 4D), with mice presenting with pulmonary adenocarcinomas (33/33 cases, 100%) and leukaemia/lymphoma (27/33 cases, 81%).