PTGS2 and colorectal adenoma: Although Cox-2 expression is restricted to the stromal cell compartment in ApcMin/+ mouse intestinal tumours9, 12, 13, 15 and is predominantly localised to stromal cells in human colorectal adenomas [10–11,14, 46–47), COX-2 is strongly expressed by malignant epithelial cells in CRCs suggesting a stage-specific switch to epithelial cell COX-2 expression11, 46.