Histological changes and immunohistochemical labeling for pericyte markers in CHMs at various gestational ages.

<p>The villi have a basophilic stroma and immature vascular structures (a, arrows) that lack a distinct lumen and do not contain hematopoietic components. Note many karyorrhectic debris in vascular structure as well as in the stroma. α-SMA expression is either not expressed (b) or is weakly (c) to moderately expressed in the villous stroma, regardless of gestational age, but not in immature vascular structures (c, arrows). In one sample, α-SMA was aberrantly detected in vascular structures (d, arrows), but not detected in the surrounding villous stroma. PDGFR-β is diffusely and strongly expressed in the villous stroma in all samples, regardless of gestational age (e), but vascular expression of PDGFR-β was rarely seen (e, arrows). Desmin shows variable levels of expression in the villous stroma, but is not detected in vascular structures (f, arrows).