IMMUNOHISTOCHEMICAL CHARACTERIZATION OF TERATOMATOUS AND FETAL NEUROENDOCRINE PANCREAS

Six extragonadal teratomas that contained pancreatic tissue were retri eved from archival material at the University of Minnesota Hospital, M inneapolis. The neuroendocrine cells were studied immunohistochemicall y for insulin, glucagon, somatostatin, pancreatic polypeptide, vasoact ive intestinal polypeptide, gastrin, chromogranin, and synaptophysin. Pancreatic tissue from autopsies of 10 stillbirths (20 to 40 weeks' ge stational age) was evaluated similarly. The features of the teratomato us pancreatic tissue were, compared with those of the fetal pancreata and with data from previous studies of normal pancreatic development a nd adult pancreata. The pancreatic tissue in ail six teratomas contain ed abundant mature islets that contained beta, alpha, delta, and pancr eatic polypeptide cells; however, they also showed widespread nesidiob lastosis with the same cell types, resembling third-trimester fetal an d neonatal pancreata. Increased proportions of alpha and delta cells w ere observed in three and five cases (relative to those of adult tissu e), respectively, providing further evidence of immaturity. Two cases showed a lack of alpha cells. None of the teratomas contained pancreat ic cells that were positive for vasoactive intestinal polypeptide or g astrin. Mechanisms that regulate neuroendocrine cell differentiation i n the normal pancreas also seem to operate in the teratomatous pancrea s; they may eventuate in features similar to those of the late fetal a nd neonatal pancreas. Abnormal differentiation in teratomas may result in deficient hormone production.