Expression of mucins, SIMA, villin, and CDX2 in small-intestinal adenocarcinoma

Expression of gastrointestinal biomarkers MUCI, MUC2, MUC5AC, small-intestinal mucin antigen (SIMA), villin, and CDX2 has been studied in colorectal adenocarcinoma (CRC). Little is known, however, about their expression in small-intestinal adenocarcinoma (SIA). We immunohistochemically compared 30 SIAs with 48 CRCs for the expression of these biomarkers. The results showed that all 6 proteins were variably expressed in SIA, but the frequencies of expression were significantly lower than those for CRC with the exception of MUC1 Specifically, positive staining for MUCI, MUC2, MUC5AC, SIMA villin, and CDX2 was observed in 16 (53%), 17 (57%), 12 (40%), 15 (50%), 20 (67%), and 18 (60%) of SlAs and 25 (52%), 43 (90%), 39 (81%), 45 (94%), 47 (98%), and 47 (98%) of CRCs, respectively. In addition, SIAs morefrequently exhibited afocal staining pattern for MUC2, MUC5AC, SIMA, and villin, whereas more diffuse immunoreactivity was evident in CRCs. Focal staining for MUCI and diffuse staining for CDX2 were common for SIAs and CRCs. Furthermore, poorly differentiated SIAs tended to express MUCI more frequently when compared with well- and moderately differentiated SIAs. These observations further support the notion that SIA is immunophenotypically distinct from CRC despite their morphologic similarity.