Villous capillary lesions of the placenta: distinctions between chorangioma, chorangiomatosis, and chorangiosis.

Chorangioma (CA), chorangiosis (CH), and chorangiomatosis (CM) are incompletely understood and overlapping villous capillary (VC) lesions believed by some to be related to hypoxia. In this study, we reviewed all cases of CA (n = 36, 0.51%) and CM (n = 39, 0.55%) diagnosed in 7,062 placentas examined at our institution between 1990 and 1999. CH was evaluated in a subsample of 689 cases (n = 46, 6.67%). Controls were derived from cases in the subsample (n = 639) without any VC lesions. Most CA were incidental findings measuring less than 0.5 cm. Nodular and multinodular morphologic variants were otherwise similar. CA were most frequently located under the chorionic plate and at the placental margins and occasionally showed nonspecific trophoblast hyperplasia (Ki-67-positive) similar to that seen in partial moles. CA and CM shared associations with preeclampia, multiple gestation, and premature delivery at 32 to 26 weeks and had a significant co-occurrence rate. Cases of CM were separated into focal, segmental, and diffuse multifocal subgroups. Diffuse multifocal CM (n = 16) showed associations with extreme prematurity (<32 weeks), congenital malformations, IUGR, delayed villous maturation, avascular villi, and placentomegaly, which were not seen in the other 2 localized subgroups. CH lacked the associations noted for CA and CM, was not increased in placentas with CA or CM, and was most frequent at greater than 37 weeks. CH was positively associated with maternal diabetes, placentomegaly, delayed villous maturation, and chronic villitis. Finally, CH lacked the continuous perivascular layer of muscle-specific actin (MSA)-positive pericytes and the multifibrillar lattice-like reticulin pattern seen in both CA and CM. In conclusion, CA and localized CM are clinically and morphologically similar lesions distinct from CH. Diffuse multifocal CM is morphologically similar to CA and localized CM, but has a distinct clinicopathologic profile.