Adrenal tissue in the placenta: a heterotopia caused by migration and embolism?

Heterotopic adrenal tissue is not uncommon, especially in the urogenital sy stem. Adrenocortical tissue in the placenta, however, is presumably very ra re. To our knowledge, four cases have been published. There are several dif ferent theories to explain such a heterotopia. According to our findings, a n embolic spread of adrenal precursor cells via fetal vascular shortcuts is the most likely mechanism. Apart from that hypothesis, the possibility of a monodermal teratoma as well as of an aberrant differentiation of cells of the extraembryonic mesoderm are considered in the literature. (C) 2000 Har court Publishers Ltd.