Pseudo-decidualization at the site of implantation in tubal pregnancy.

The tissue from three tubal pregnancies at the site of implantation has been investigated with light and electron microscopy. Large seemingly "decidual" cells were found to be present between the anchoring villi and the tissue of the uterine tubes. These cells are or cytotrophoblastic column origin. Through discontinuities of the syncytiotrophoblast they migrate into the underlying tissue were they grow and synthesize large amounts of glycogen. It is suggested that these cells be named pseudo-decidual cells in order to distinguish them clearly from genuine decidual cells to which they only bear a resemblance on the light microscopical level. The fibrinoid present at the utero-placental interface in ectopic implantation cannot be found in ectopic implantation. From this fact it is deduced that fibrinoid is formed through the action of genuine decidual cells and therefore must be of maternal origin.