Application of the Papanicolaou stain to routine histological examination of placenta.

Since its introduction by Papanicolaou (1942), the Papanicolaou staining procedure has gained universal acceptance in cytological examinations. In routine vaginal cytological preparations the Papanicolaou stain demonstrates monilia species and a number of different organisms, and also provides excellent cytological staining of both nucleus and cytoplasm. Chorioamnionitis is one of the commonest abnormalities seen in placental specimens, and the organisms involved are usually those present in the vagina. It seemed logical, therefore , to use the Papanicolaou staining procedure to study placental histology. Material and methods In the initial stages of the study, selected cases of monilial chorioamnionitis, toxoplasmosis, cyto-megalovirus placentitis, and other viral placentitides were selected. To these cases, the placentae with chorangiomata, infarcts, meconium staining, amnion nodosum, bacterial chorioamnionitis, and placentae from mothers with gestational diabetes were added. Results We were surprised by the quality of the results of the Papanicolaou stain. Monilia species were demonstrated as fine delicate pseudohyphae invading the tissue in a case of monilia chorioamnionitis and funisitis. Toxoplasma pseudocysts stained a distinctive orange-brown and could be separated clearly from other structures. Papanicolaou-stained sections gave excellent nuclear and cytological detail, and this enabled an extremely ready recognition of plasma cells in the chorionic villi in a case of cytomegalo-virus infection, and when inclusion bodies were present they, too, were readily identified. Excellent histological delineation of the structure of a chorangioma was obtained and infarcts were clearly delineated by the technique. In an infant whose mother had suffered from pre-eclamptic toxaemia, evidence of atherosis of the decidual basal vessels was identified fairly readily with this particular technique. In addition to these obvious advantages of the Papanicolaou stain, most of which could be predicted , certain additional bonuses were obtained. In cases of chorioamnionitis, prominent eosinophilic degeneration of the subepithelial layers of mesen-chyme below the amniotic epithelium were readily apparent; cases of vernix granuloma were easily identified, and the residual squames within the granulomata stained strongly eosinophilic. Islands of squamous metaplasia, not surprisingly, were extremely readily identifiable in varying stages of their development, and, when present, deposits of calcium stained a rather stiking hue of haematoxo-philic blue. In addition, it was apparent that the Papanicolaou acts very much like a trichrome stain in distinguishing smooth muscle cells, which stain distinctively, from the nondescript blue-green of the undifferentiated mesenchyme. This was of particular use in the study of vascular lesions occurring in the fetal chorionic circulation. Pigmented meconium-containing cells …