The immunophenotype of human decidua and extra-uterine decidual reactions.

Decidua associated with products of conception from intra-uterine and extra-uterine gestations and decidualized tissue from the appendix, cervix and Fallopian tube were studied using a panel of antibodies and antisera. Immunolocalization of vimentin and desmin intermediate filament proteins and of alpha-1-antitrypsin and alpha-1-antichymotrypsin was identified in most of the 43 cases studied. Placental alkaline phosphatase, beta human chorionic gonadotrophin, cytokeratin, smooth-muscle actin and leukocyte markers (CD3, CD20, CD68) were also expressed in some cases. Occasional cases reacted for CD45 and S-100 protein. Similar reaction profiles were obtained at both intra-uterine and extra-uterine sites. The results show that extra-uterine mesenchymal cells which have undergone a decidual reaction correspond closely to their counterparts in the endometrial stroma. Since positive immunostaining within decidual cells for cytokeratins, placental alkaline phosphatase and beta human chorionic gonadotrophin indicates that trophoblastic cells are not exclusively recognized by these antibodies, their use does not permit the confident diagnosis of an intra-uterine gestation.