Immunohistochemical staining of human pancreatic tumor tissues. Frozen sections of ductal pancreatic adenocarcinomas (A and C) were stained with MORAb-009. Membranous staining at the luminal and apical surface of neoplastic cells was detected. (B and D) Five-fold enlargement of dotted areas in A and C. Shown are clusters of neoplastic cells where approximately 75% of the cells stained positive with MORAb-009.