Cytokeratin expression profile in gastric carcinomas.

Cytokeratin (CK) is observed mainly in epithelial cells, and the diverse expression pattern of CK subtypes may be helpful in discriminating between primary and metastatic carcinomas in various organs, including the stomach. To clarify the CK expression profiles in gastric carcinomas, 329 consecutive specimens were immunohistochemically evaluated in terms of their CK subtypes using the tissue array method. The overall positive rates were 84.7% for CK4, 3.2% for CK5, 28.7% for CK6, 71.1% for CK7, 96.6% for CK8, 0% for CK10, 81.6% for CK13, 0.3% for CK14, 4.1% for CK16, 0% for CK17, 99.4% for CK18, 89.7% for CK19, and 30.0% for CK20. Well-differentiated or moderately differentiated carcinomas were related to several CKs, and mucinous carcinoma was associated with CK20 expression. Interestingly, CK7 and CK20 expression was associated with the mucin phenotype of gastric carcinoma, but this association had no diagnostic value. Epstein-Barr virus (EBV)-associated gastric carcinomas showed a tendency toward negative expression of CK7. CK6 expression was related to microsatellite instability (MSI), early pTNM stage, and better clinical outcome. In conclusion, CK expression profiles in consecutive gastric carcinomas demonstrate heterogeneity, and no single CK has diagnostic value by itself. CK expression is associated with various clinicopathologic parameters, mucin phenotype, EBV positivity, MSI status, and patient survival.