Immunohistochemical detection of RBFOX1. (A) Normal appearing colonic mucosa with diffuse cytoplasmic staining of most epithelium (x100). (B) Normal colon with diffuse staining of the epithelium and some stromal cells and inflammatory cells; the pericryptal sheath fibroblasts appear unstained (x200). (C) Adenocarcinoma showing absence of RBFOX1 staining in the majority of the cells lining the two-neoplastic glands in the lower half of the picture (x200). (D) Neighbouring glands show persistence (left) or reduction/ loss (right) of RBFOX1 immunoreactivity on epithelial cell cytoplasm (x200).