Rediscovering Langhans' Fibrinoid Layer: A Forgotten Barrier at the Maternal–Fetal Interface

In placental histopathology, the Langhans' fibrinoid layer holds a unique but often overlooked position. Although it was described over a hundred years ago and featured in classic medical texts, it has gradually faded from modern research. Langhans' fibrinoid is one of the most underappreciated and inconsistently described parts of placental structure. In this article, we revisit its historical roots, anatomical ambiguity, and potential clinical significance, aiming to give it a clear and updated definition in current placental studies and diagnostics.