OPEN NEURAL-TUBE DEFECTS - IMMUNOCYTOCHEMICAL DEMONSTRATION OF NEUROEPITHELIAL CELLS IN AMNIOTIC-FLUID

Cytologic evaluation of second trimester amniotic fluid (AF) is ct rap id, inexpensive adjunct to prenatal diagnosis of open neural tube defe cts (ONTDs). Ou, goal was to determine whether the neural-appearing ce lls and/or large foamy macrophages irt the AF of anencephalics are ind eed of neural and/or glial origin. I two second trimester patients wit h elevated serum alpha-fetoprotein (AFP) and polyhydramnios, fetal son ogram studies showed anencephaly; amniocentesis was performed for AF-A FF cytogenetic, and cytologic studies. AF sediment smears were initial ly Papanicolaou-stained; next, the same smears were immunoperoxidase ( IP)-stained for glial fibrillary acidic protein (GFAP). if GFAP negati ve, slides were restained for synaptophysin (SYN) and neuron-specific enolase (NSE). Both AFs contained small neural-appearing cells (5-10 m u m) singly and in clusters, with dense, round, homogeneous nuclei, ar t occasional nucleolus, and scant cytoplasmic rim. These were GFAP neg ative and SYN and NSE positive; the large vacuolated, lipid-laden macr ophages (20-40 mu m) were negative for all three IP stains. In conclus ion, positive IP staining for SYN and NSE supports the morphologic imp ression that small dark cells in AF are of neural origin, while negati ve IP staining of large foamy macrophages suggests nonneural, nonglial origin. (C) 1997 Wiley-Liss, Inc.