Loss of heterozygosity and genomic instability in synchronous endometrioid tumors of the ovary and endometrium

Background. The unknown etiology of endometrioid carcinomas of the ovary and the relatively high frequency of a concomitant carcinoma of the endometrium in these patients warrants study of such tumors. The aim of this study was to identify the genetic alterations involved in endometrioid ovarian cancer development, and to determine whether primary tumors of the endometrium and synchronous primary endometrioid tumors of the ovary could be distinguished based on differing patterns of genetic alterations. The distinction of metastatic carcinoma of the ovary from other synchronous primary tumors is often difficult but has important therapeutic and prognostic implications. Methods. This study examined the genetic alterations at 28 polymorphic DNA markers in the DNA of tumors of 17 patients with endometrioid carcinoma of the ovary, including 5 nonmetastatic ovarian tumors, 5 ovarian tumors metastatic to the uterus, and 7 endometrioid ovarian tumors with a synchronous primary endometrial tumor. Results. Chromosomes 17 and 22 were found to be the most common sites of loss of heterozygosity (LOH) in the 17 patients studied. Loss of heterozygosity on chromosome 17 was associated with advanced stage ovarian tumors. In 96% of LOH events in the metastatic tumors, LOH was observed in the primary tumor and in the metastatic site. Conversely, in four of seven synchronous tumors in which LOH was observed, LOH was confined to the ovarian tumor. Genomic instability was identified in two of seven patients with synchronously occurring tumors that did not demonstrate LOH. A positive family history was noted for these two patients. Conclusions. A lack of shared genetic alterations and in synchronously occurring endometrial and endometrioid ovarian tumors indicates independent developmental pathways for these tumors. Loss of heterozygosity on chromosome 17 in endometroid ovarian carcinoma may indicate transition to a more aggressive tumor. Cancer 1995; 76:650–7.