AN IMMUNOHISTOLOGIC STUDY OF THE FETO-ACINAR PANCREATIC PROTEIN (FAP) IN THE NORMAL PANCREAS, CHRONIC-PANCREATITIS, PANCREATIC ADENOCARCINOMA, AND INTRAABDOMINAL METASTASES OF ADENOCARCINOMAS

The immunohistologic distribution of the feto-acinar pancreatic protein (FAP), detected by the monoclonal antibody (MoAb) J28 using an indirect immunoperoxidase technique, is described. Tests were carried out on normal adult pancreas (n = 10), chronic pancreatitis (n = 14), pancreatic adenocarcinoma (n = 17), intraabdominal metastases of pancreatic and nonpancreatic origin (n = 22), metastatic tumors invading the pancreas (n = 3), non-pancreatic fetal (n = 39) and adult (n = 65) normal organs (n = 104), and nonpancreatic malignancies (n = 145). All sections were formalin fixed and paraffin embedded. In the normal pancreas, only a few positive acinar cells were found around some islets of Langerhans. In pancreatitis there was an increased expression of FAP protein in the acinar tissue in relation to inflammatory changes. In cases of primary pancreatic adenocarcinoma and metastatic tumors in the pancreas, a strong expression of FAP protein in the peritumoral acinar area was found. The tumors themselves were FAP protein negative, as were the nonpancreatic tumors and normal organs. It can be concluded that FAP protein, detected by MoAb J28 in tissue sections, is specific for pancreatic exocrine tissue with reactive changes.