CAM 5.2 is a murine monoclonal antibody, raised against the colon carcinoma cell line HT29, which recognises lower molecular weight intracellular cytokeratin proteins within secretory epithelia. Extensive indirect immunohistochemical studies have confirmed that this antibody stains formalin fixed (and freshly frozen) normal and malignant human tissue in a consistent manner. Reliable staining of conventionally processed pathological tissues provides more accurate identification and staging of human malignant epithelial diseases.