Intrauterine fetal demise due to multifocal chorangiomatosis of the placenta
Three benign, interrelated vascular lesions have been identified in the placenta-chorangiosis, chorangiomatosis and chorangioma. All three of these lesions have overlapping histologic features. Chorangiosis and chorangioma are the more established lesions. Chorangiosis is defined by the Altshuler criteria (often called "the rule of 10s") as the presence of more than 10 capillaries per distal villus in at least 10 villi per 10X field, in at least 3 different, non-infarcted regions of the placenta. This hypercapillarization is thought to arise from increased elongation and coiling of terminal villous capillaries. Although the etiology of chorangiosis is not settled, this lesion is felt to represent an adaptive response to hypoxia or chronic inflammation.
Chorangioma is defined as capillary vascular channels forming an expansile nodular lesion, also containing intervening stromal cells and surrounded by a layer of trophoblast. The nodule is a coherent unit of capillary vascular channels, and the channels do not permeate normal villous structures. Chorangiomas are typically solitary and small (<1 cm), although the occurrence of multiple chorangiomas has been reported. Large lesions are seen rarely. These larger lesions may be associated with maternal or fetal complications, including intrauterine fetal demise.
The lesion in this case-chorangiomatosis-is the most poorly defined and least studied of the three placental vascular proliferations. In the older literature, these lesions were subsumed within the chorangioma category. Although there are overlapping features, recent efforts have attempted to separate chorangiomatosis from chorangiomas. Histologically, chorangiomatosis is characterized by capillary vascular lesions that permeate larger villous structures. The lesions are set in a background of increased stromal collagenization and cellularity. Immunohistochemical staining of the stroma often reveals vimentin positive cells surrounded by dense reticulin fibers.
Chorangiomatosis can be separated into focal, segmental and diffuse multifocal. The clinical features of the mothers and infants of placentas with the focal and segmental variants are similar to those with placental chorangiomas. The diffuse multifocal variant appears to be quite different, however. In particular, diffuse multifocal chorangiomatosis is associated with more severe fetal complications, including extreme prematurity (<32 weeks), congenital malformations, intrauterine growth restriction and intrauterine fetal demise. In addition, the placentas from these cases also show delayed villous maturation, avascular villi and placentomegaly (>90 percentile).
The incidence of multifocal chorangiomatosis is uncertain. Likewise, the rate of recurrence is unknown. Of significance, however, a handful of case reports identifying recurrent multifocal chorangiomatosis in subsequent pregnancies can be found.
Contributed by Lananh Nguyen, MD and W. Tony Parks, MD