Searching against our in-house database (http://bioinfosrv1.bmb.uga.edu/DMarker/) which includes public microarray datasets from GEO [17], Oncomine [18] and SMD [19], covering over 53 human diseases including cancer, we found that the differential expression patterns of 15 genes are highly specific to gastric cancer, such as GKN2, CLDN7, THY1, GIF and PGA4, while most others are general to multiple cancer types. The gene discussed is PGA4; the disease is gastric cancer.