In the second model, Adenoviral-Cre infusion during laparotomy into the distal colons of three month old double homozygous ApcLoxP/LoxP Msh2 LoxP/LoxP mice enables reliable spontaneous adenoma formation in the large intestine that can be subsequently followed by endoscopy and other types of imaging without sacrificing the mice. Here, MSH2 is linked to adenoma.