Chorangioma. A cytoskeletal profile.

Cytoskeletal typing of five chorangiomas revealed diffuse staining of the blood vessels with antibodies to vimentin and to alpha smooth muscle (alpha-SM) actin, while cytokeratin 18 decorated the blood vessels focally. Focal staining for desmin was observed in two chorangiomas. Blood vessels of the placentas in which these chorangiomas arose stained for vimentin and alpha-SM actin. In addition, there was positive staining for cytokeratin polypeptide 18 in blood vessels within the chorionic plate and anchoring villi, and occasional staining for desmin. The vasculature of the terminal villi lacked cytokeratins. The stromal elements of the chorangiomas stained for vimentin and focally for alpha-SM actin and cytokeratin 18. A similar staining pattern was also found in the placental stroma, with most of the cytokeratin positivity encountered in the chorionic plate and anchoring villi. Blood vessels in extraplacental hemangiomas were devoid of cytokeratins. These results indicate that chorangiomas originate most likely from blood vessels of the chorionic plate and anchoring villi, which, as chorangiomas, are the site of vascular cytokeratin expression.