Frequency of hyperdiploid chromosome complements in endometrioid tumors of the endometrium whereas similar tumors in the ovary tend to show hypodiploidy: a significant difference that may not be distinguishable by flow cytometry of DNA content.

Recent interest has focused on endometrioid carcinomas of the endometrium in view of the frequent occurrence of microsatellite stability, accompanied by a favorable prognosis, and by near-diploidy when studied by flow cytometry. The latter feature fails to address the question whether (and to what extent) the karyotypes of the tumor cells may or may not be truly diploid, an important feature on which there is virtually no information. A reconsideration of earlier published and unpublished work in this laboratory on near-diploid carcinomas of the endometrium, and comparable studies on near-diploid ovarian carcinomas (a site where endometrioid carcinomas are also commonly found) has therefore been undertaken. In the endometrium, these studies have clearly shown that carcinomas with near-diploid chromosomes are in fact commonly hyperdiploid, often of endometrioid histology, and in many instances show a single additional chromosome, differing in different tumors, as the apparently sole chromosome change. By contrast, similar studies on the ovary (which also included several endometrioid carcinomas) revealed a tendency towards hypodiploidy, with loss of a few chromosomes, as well as the presence of structural chromosome changes and a generally poor prognosis.