Figure 17. The villi in this case of chickenpox associated chronic villitis shows a Langhans-type giant cell (arrow), a chronic granulomatous villitis. This cell is believed to be the product of a fusion of macrophages, just as in other disease conditions. The majority of the villous stroma is composed of cells of monocyte/macrophage lineage. It is believed these cells provide some protection to the fetus from hematogenous viral transmission across the placenta. Most cases of chronic villitis, even with so-called granulomatous changes, cannot be clearly tied to an etiologic infectious agent, and are "non-specific".