The mucin appears clear in stains, but it is diastase resistant, periodic acid-Schiff and mucicarmine positive.[8,9] In Goldstein et al's[10] study on 27 cases of gastric signet-ring cell carcinoma, the expression status of CK7/20 was very similar to that in the present study, and this previous study suggested that the CK7/20 pattern is useful in determining the primary and metastatic origin of this carcinoma. This evidence concerns the gene MUC5AC and carcinoma.