Immunostaining of the chorionic villi in tubal pregnancy. Expressions of estrogen receptor (ER)-alpha (A, B), progestogen receptor (PR) (C, D), leukemia inhibitory factor (LIF) (E, F), vascular endothelial growth factor (VEGF) (G, H), inducible nitric oxide synthase (iNOS) (I, J) and endocannabinoid receptor (CB1) (K, L) in the chorionic villi observed by immunohistochemistry. Positive staining was detected in the chorionic villi from both the LNG-EC group (A, C, E, G, I) and the control group (B, D, F, H, J). The immunostaining for ER-alpha (A, B) and PR(C, D) was observed in the nuclei of cytotrophobast, syncytiotrophoblast, and stromal cells from both groups. The immunostaining for LIF (E, F), VEGF (G, H), iNOS (I, J) and CB1 (K, L) was seen in the cytoplasm of cytotrophobast, syncytiotrophoblast, and stromal cells from both groups. There were no significant differences between the two groups in the expressions of ER-alpha (A, B), PR (C, D), LIF (E, F), VEGF (G, H), iNOS (I, J) or CB1 (K, L). Magnification: 400×.