Synchronous endometrial and ovarian carcinoma (SEOC) is a rare instance but it accounts for 50–70% of all synchronous female genital tract tumors. Due to the different management and the favorable prognosis of SEOCs, it is important to separate SEOCs from a metastatic disease.

Endometrial carcinoma (EC) and ovarian carcinoma (OvCa) are two common female cancers, accounting for 4th and 5th-leading causes of cancer death among women in the United States (Siegel, Miller & Jemal, 2019). EC can be divided into two subgroups, a type I endometrioid tumors and a type II serous-like tumor (Getz et al., 2013). Compared to type I EC, type II serous-like EC was characterized with a more advanced stage and worse outcome. As for ovarian cancers, high grade OvCa serous tumors account for the most cancer death (Matulonis et al., 2016). Previous studies have identified similar genetic aberrations among serous-like EC and serous OvCa (Getz et al., 2013). For example, both serous-like EC and serous OvCa have frequent TP53 mutation, whereas type I endometroid EC does not. Also, serous-like EC and serous OvCa are both featured with chromosome instability and copy number alteration (CNA), compared to very few CNA events in type I endometroid EC. These findings suggest that they might be caused by similar oncogenic drivers and more importantly, share common molecular mechanisms for tumor progression.