Tissue with fissioning crypts stained for Pms2 (A), Ercc1 (B) and Xpf (C). These sequential sections were from histologically normal tissue marginal to a resected sigmoid adenocarcinoma of a female patient. There appear to be fissioning crypts in this area of tissue, indicated by arrows. These fissioning crypts have reduced expression for each of the three proteins, Pms2, Ercc1 and Xpf. Most of the other crypts in this area have high expression of Pms2, Ercc1 and Xpf in their cell nuclei. These fissioning crypts may constitute a small patch of DNA repair-defective crypts that are increasing in patch size by crypt fission. Images taken at 200×.