Partial hydatidiform mole in a pregnant chimpanzee (Pan troglodytes)

Until now, the occurrence of hydatidiform mole in non‐human primates has not been documented. This report presents a case in which a stillborn fetus, associated with a partial hydatidiform mole, was found at necropsy in the uterus of a pregnant chimpanzee ( Pan troglodytes ) which had suddenly died. Hydropic swelling of the chorionic villi and proliferation of trophoblastic cells were present. The trophoblast was stained enzyme‐immunohistochemically with human chorionic gonadotropin (hCG) and pregnancy‐specific‐β1‐glycoprotein (SP1). The concentrations of hCG and SP1 in maternal serum were high, 1,350 mIU/ml and 1,000 ng/ml, respectively. The distribution of DNA content of the cytotrophoblast in the molar villi shifted from diploid to an aneuploid pattern.