CDX-2, cytokeratin 7 and cytokeratin 20 immunohistochemical expression in the differential diagnosis of primary adenocarcinomas of the sinonasal tract.

Because the histopathological features of some primary adenocarcinomas of the sinonasal tract may show considerable overlap, we assessed the diagnostic value of a panel of immunohistochemical markers in the distinction between these malignancies. Paraffin-embedded tumour tissue sections from a series of 39 primary adenocarcinomas of the sinonasal tract, including 25 cases of intestinal-type adenocarcinoma (ITAC), 10 cases of salivary gland-type carcinoma and 4 cases of tubulopapillary low-grade adenocarcinoma were immunostained for CDX-2, cytokeratin 7 and cytokeratin 20. Diffuse nuclear staining for CDX-2 was identified in 80% of ITACs, while all non-ITACs were negative. Staining for cytokeratin 20 was positive in 84% of ITACs, including all cases negative for CDX-2, but negative in all other adenocarcinomas. Cytokeratin 7 was consistently positive in 88% of ITACs and in 100% of non-ITACs. Normal sinonasal epithelia expressed cytokeratin 7, but not CDX-2 and cytokeratin 20. Staining for CDX-2 and cytokeratin 20 has potential use in separating ITACs from other primary malignant glandular neoplasms of the nasal cavities and paranasal sinuses.