An immunohistochemical study of primary signet-ring cell carcinoma of the stomach and colorectum: I. Cytokeratin profile in 42 cases.

Expression of cytokeratin (CK) profiles in primary signet-ring cell carcinoma (SRCC) of the stomach and colorectum have rarely reported; only two such studies are present in the world literature. Herein, an immunohistochemical study on cytokeratin (CK) expression was performed in 42 cases of primary SRCC of the stomach (30 cases) and colorectum (12 cases). SRCC was defined as an adenocarcinoma in which more than 50% adenocarcinoma cells showed SRCC phenotype with prominent intracytoplasmic mucins. In the gastric SRCC, the expression of CK was as follows; CK AE1/3 (30/30, 100%) CK CAM5.2 (30/30, 100%), CK 34BE12 (0/30, 0%), CK5/6 (2/30, 7%), CK7 (26/30, 89%), CK8 (12/30, 40%), CK14 (0/30, 0%), CK18 (30/30, 100%), CK19 (2/30, 7%), and CK20 (3/30, 10%). In the colorectal SRCC, the expression of CK was as follows; CK AE1/3 (12/12, 100%) CK CAM5.2 (12/12, 100%), CK 34BE12 (0/12, 0%), CK5/6 (0/12, 10%), CK7 (2/12, 17%), CK8 (3/12, 25%), CK14 (0/12, 0%), CK18 (12/12, 100%), CK19 (7/12, 58%), and CK20 (8/12, 67%). A statistical analysis showed that significant differences of CK expression between the gastric SRCC and colorectal SRCC were observed in CK7 (stomach 67% vs. colorectum 17%), CK19 (7% vs. 42%) and CK20 (13% vs. 67%); gastric SRCC tended to express CK7, but not CK19 and CK20, while colorectal SRCC tended to express CK19 and CK20, but not CK7. In gastric SRCC, CK7+/CK20- pattern was as follows: CK7+/CK20- (24/30, 81%), CK7+/CK20+ (2/30, 6%), CK7-/CK20+ (1/30, 3%), and CK7-/CK20- (3/30, 10%). CK7/CK19 patterns in gastric SRCC were as follows; CK7+/CK19- (25/30, 83%) CK7+/CK19+ (1/30, 3%), CK7-/CK19+ (1/30, 3%), CK7-/CK19- (3/30, 10%). In colorectal SRCC, the CK7/CK20 patterns were as follows: CK7+/CK20- (2/12, 17%), CK7+/CK20+ (0/12, 0%), CK7-/CK20+ (8/12, 66%), and CK7-/CK20- (2/12, 17%). The CK7/CK19 pattern in colorectal SRCC was as follows; CK7+/CK19- (1/12, 8%), CK7+/CK19+ (1/12, 8%), CK7-/CK19+ (6/12, 50%), and CK7-/CK19- (4/12, 34%). Statistical data indicated that CK7+/CK20- and CK7+/CK19- patterns were significantly prevalent in gastric SRCC, and CK7-/CK20+, CK7-/CK19+ and CK7-/CK20- patterns dominated significantly in colorectal SRCC. CK expression has been studied largely in terms of CD7/CK20 expression pattern in various carcinomas. The present study provided possible usefulness of CK7/19 expression status in various carcinomas including SRCC.