A Reassessment of Chorionic Histiocytic Hyperplasia in Association With Other Inflammatory Lesions of the Placenta.

Background: Chorionic histiocytic hyperplasia (CHH) is a chronic inflammatory lesion (CIL) with a linear infiltrate of fetal histiocytes in the base of fetal or membranous chorion. We performed a retrospective study of placentas diagnosed since our last study period in order to analyze the strength of the association of CHH with other CIL.

Methods: Third trimester placentas diagnosed with CHH were identified in our LIS. Comparisons of incidence of associated lesions, including chronic villitis (CV), chronic deciduitis (CD), chronic chorioamnionitis (CC), eosinophilic/T-cell chorionic vasculitis (ETCV), and maternal and fetal acute inflammatory responses, between the prior and current studies were evaluated using the chi square statistic.

Results: CHH was present in 2.2% of placentas, significantly higher than 1.3% in the prior study period. A majority of CHH cases had accompanying CV (82.3%). CD was more often associated with CHH in the current study than in the prior study (49.1% vs 40.0%).

Conclusions: The greater incidence of CHH in third trimester placentas diagnosed in the past 7.5 years may be due to greater recognition of the lesion by our pathologists. This study demonstrated the need for more research of CIL.