In the 2 cases, the mesothelial immunological indicator (Calretinin, CK5/6, WT-1, and D2-40) findings were positive, which was needed to make the differential diagnoses of well-differentiated papillary mesothelial tumor, a borderline tumor and mesothelioma, a malignant tumor. This evidence concerns the gene CALB2 and mesothelioma.