[A rare placental lesion: Intraparenchymal hepatic heterotopia]

Intra-placental hepatic heterotopia is a rare lesion of embryonic development, poorly understood and often discovered incidentally during histopathological analyses. The morphological aspects of this lesion, as classically described, are relatively consistent in the literature, and several etiopathogenic hypotheses have been proposed, though none is entirely satisfactory. We report the case of a placenta presenting multiple foci of hepatic heterotopia identified within the fetal vascular network. The observation concerns a patient whose pregnancy was medically terminated at 20 weeks of amenorrhea due to a fetal polymalformative syndrome, for which a post-mortem diagnosis of Noonan syndrome was established. The pathological examination revealed three placental parenchymal lesions corresponding to heterotopic hepatic tissue. To date, no risk factors have been reported in the literature, nor have any known consequences on the child's development been identified. However, Noonan syndrome is recognized as a risk factor for the development of pediatric hepatic adenomatous lesions. The association of these two lesions may be coincidental or may support the etiopathogenic hypothesis of secondary migration of a hepatocellular adenoma within the fetal vascular network. The etiopathogenic mechanisms remain debated: an aberrant migration of hepatic tissue fragments through intra-vascular embolism, the entrapment of hepatocytes by the yolk sac, or even a co-evolution of the placenta and liver from stem cells. The absence of tumor characteristics and the histological similarity with embryonic hepatic tissue support the hypothesis of hepatic cell migration within the placenta.