Human teratocarcinoma has lengthy held a fascination to the pathologist be reason behind the range of the doubtless benign differentiated tissues asso ciated with the tumor. An knowing of this range got here with the demonstration of the pluripotent nature of the embryonal carcinoma telephone, the stem cellphone of the tumor, in experimental animals. unmarried mobile clones of murine embryonal carcinomas have been derived and the consequent telephone strains injected into immunosuppressed hosts, the place the embryonal carcinoma stem phone itself gave upward push to the wealth of differentiated tissues noticeable in teratocarcinomas. It was once additionally proven that teratocarcinomas might be professional duced experimentally through transplantation of staged early mouse embryo to extrauterine websites; next experiments urged that the embryonal carcinoma stem cellphone used to be, in reality, reminiscent of a regular cellphone of the em bryonic ectoderm. Many based experiments have seeing that been outfitted in this early paintings; murine embryonal carcinoma cells are delivering the ex perimental fabric for a primary biochemical evaluate of the earliest dif ferentiation occasions in mammalian embryogenesis. during this quantity, we relate the beginnings of experimental examine on human teratoma. The human embryonal carcinoma cells were char acterized and confirmed in vitro, supplying an experimental version to check the original biology of those cells. Monoclonal antibodies, estab lished from paintings with those in vitro cultures, supply telephone floor probes that outline populations of embryonal cells and their derivatives in tumor sections.