Expression of CDX2, cytokeratins 7 and 20 in sinonasal intestinal-type adenocarcinoma

CDX2 is a transcription factor expressed by intestinal epithelium. It is considered as a sensitive marker for a colorectal or-less frequently-gastric origin of adenocarcinomas. The pattern of coordinated expression of cytokeratin (CK) 7 and CK20 is also useful for the diagnosis of the origin of metastatic adenocarcinomas. Expression of CDX2, CK7 and CK20 was investigated in 14 cases of sinonasal intestinal-type adenocarcinoma (SIA), a particular tumor with an enteric-cell-type appearance. Formalin-fixed, paraffin embedded tissue sections were immunostained with monoclonal antibodies using the biotin-labeled streptavidin technique. All of the cases expressed CDX2, being stained 50 to 100% of the tumor cells (mean: 87.2%). CK7 positivity was detected in 8 cases (57.1%), with the staining of 10 to 100% of cells (mean: 65.6%), and CK20 was found in all the tumors (10 to 100% of cells; mean: 78.8%). The histologic resemblance between SIA and colorectal adenocarcinoma is reinforced by the expression of CDX2 and CK20, which are virtually constant in both neoplasms. CDX2 seems to be a marker for cellular phenotype better than an indicator of the origin of adenocarcinomas. CK7 is expressed in SIA less frequently than in colonic adenocarcinoma, but with a rate similar to the subset of rectal tumors, making the differential diagnosis between the two neoplasms difficult.