CDX2

CDX2 is a very useful marker of colorectal differentiation, most often employed in the work-up of tumors of unknown origin. Positive staining is seen in 80 – 100% of colorectal carcinomas, but slightly less if the tumor is poorly differentiated. However, staining may also be seen with gastric adenocarcinomas (35-70%), small intestinal adenocarcinomas (60%), extrahepatic bile duct carcinomas (37%), GI carcinoid tumors, and some mucinous carcinomas of the lung, ovary, endometrium and cervix; therefore, additional stains should be employed to complement the lack of specificity    –     

(Am J Surg Pathology 2003;27:303, Arch Pathology Lab Med 2005;129:920).