Immunophenotypic differences between intestinal-type and low-grade papillary sinonasal adenocarcinomas - An immunohistochemical study of 22 cases utilizing CDX2 and MUC2

Nonsalivary sinonasal adenocarcinomas can be divided into low-grade and high-grade tumors. The former are often papillary and the latter are usually of intestinal type, morphologically similar to metastatic colonic carcinoma. Antibodies to CDX2, a transcription factor gene highly specific for intestinal adenocarcinomas, MUC2, a mucin gene expressed in adenocarcinomas from various sites, and cytokeratins (CK) 7 and 20 were used to examine the two groups of tumors. Formalin-fixed, paraffin-embedded tissue from 22 sinonasal adenocarcinomas was reclassified into 9 high-grade intestinal-type, 3 high-grade nonintestinal, and 10 low-grade, predominantly papillary adenocarcinomas. Immunohistochemical staining was graded on a 0 to 4+ scale with 5% or greater tumor cell staining considered positive. Of the high-grade intestinal group, 78% demonstrated 4+ CDX2 positivity, with 44% MUC2 positive. Although 89% of this group was CK7 positive, the percent of staining was variable. A majority (67%) of the intestinal cases was 4+ CK20 positive. Almost every nonintestinal adenocarcinoma (90%) (low- and high-grade) was CK7 positive (7 of 9, 4+), without expression of any of the three colonic adenocarcinoma markers. The three high-grade nonintestinal tumors had the expression profile of the low-grade papillary group with the exception of focal MUC2 positivity in 1 case. Intestinal-type adenocarcinomas have an expression profile distinct from nonintestinal sinonasal adenocarcinomas. The former are similar, but not identical, to colonic adenocarcinomas. Immunohistochemical staining for CDX2, MUC2, and differential cytokeratins does not differentiate metastatic colorectal from primary sinonasal intestinal-type adenocarcinoma.