We analysed 23 snap-frozen colorectal tissue samples of normal mucosa, adenomas and untreated invasive carcinomas by the SA-β-gal assay, complemented by immunostaining for the proliferation marker Ki67 and confirmed the reportedly high frequency of senescent cells in adenomas, leading to the classification of 8 out of 12 adenoma cases tested as senescent, which is well in line with their macroscopic presentation as polyps of often stable size for years (Figure 1A and B; see the flow diagram in Figure 2A for technical details) (Bartkova et al, 2006). This evidence concerns the gene MKI67 and invasive carcinoma.