Acute Mst1/Mst2 deletion in the adult liver, achieved either by intravenous injection of adenovirus expressing Cre recombinase (Zhou et al, 2009), or by tamoxifen induction of MMTV–CreERT or CAAGS–CreERT (Lu et al, 2010; Song et al, 2010) produced an intermediate tumour phenotype consisting of both HCC and mixed HCC/CC histology. The gene discussed is MST1; the disease is cholangiocarcinoma.