abnormal trophectoderm morphology abnormal polar trophectoderm morphology MPheno.ontology csmith any structural anomaly of the trophectoderm portion that surrounds the inner cell mass (ICM); unlike mural trophectoderm cells which stop proliferating and become large polyploid cells (the primary trophoblastic giant cells) by endoreduplication, polar trophectoderm cells remain diploid, continue to proliferate and give rise to both the ectoplacental cone and the extraembryonic ectoderm MP:0012056 2013-08-09T09:21:13Z