The BeWo trophoblastic cell line was the first human endocrine cell type. A human choriocarcinoma sample was taken at autopsy from a cerebral metastasis; cells were initially transplanted to the cheek pouch of a hamster and maintained by serial passage for 8 years prior to growth in culture vessels. The cell line can express hormones, progesterone, human chorionic gonadotropin (hCG), human chorionic somatomammotropin (placental lactogen), estrogen, estrone, estriol and estradiol. The cells are positive for keratin by immunoperoxidase staining.