Aim: To address the dearth of published information on the cytomorphology of the normal, term human placenta.
Materials and Methods: Following delivery, term placentas from normal pregnancies were sampled using fine needle aspiration (FNA) and direct scrapes. Air dried smears were stained with Giemsa and CytoLyt suspensions prepared as cytospins and ThinPrep slides were stained with Papanicolaou. Residual material was used to generate formalin fixed paraffin embedded cell blocks and cut as H&E sections. Standard histological examination was also performed for correlation and to exclude pathological changes.
Results: Fifty slides were generated for evaluation. Direct smears, cytospins, ThinPrep slides and cell blocks all demonstrated preserved villous architecture however air dried Giemsa slides were superior for visualisation of arborising villi in microbiopsies. Surface trophoblast appeared stripped in cytospin and ThinPrep samples with sheets of irregularly placed nuclei and clusters of naked syncytiotrophoblast nuclei appearing in the background. Nuclear chromatin appeared finely clumped in all preparations but was best appreciated in Pap stained cytospins. Vasculature was difficult to visualise in samples other than cell block sections. Fibriniod material was noted in all preparations.
Placental cytomorphology has previously not been well described and we have shown that a combination of preparations and stains provide a comprehensive presentation of all aspects of placental cytomorphology. On this basis we propose that placental FNA sampling may represent an untapped resource for evaluation of anomalies of villous architecture and trophoblast function linked to pregnancy complications such as preeclampsia, fetal growth restriction and stillbirth.