Cancer diagnosis and classification have traditionally been based on the assessment of morphology by microscopy. However, the histological classification system is challenging and demand for genetic information is increasing in the era of targeted and personalized molecular therapy. Recently accumulated comprehensive genomic data could be used to provide a molecular cancer classification alongside the histological classification. This study identified a 19 gene signature able to classify endometrial cancers into the two major histological subtypes, endometrioid and serous. In addition, when the genomic classifier was applied to endometrioid adenocarcinoma of high grade (EM-HG), a subset (23.6%, 25/106) was predicted to be similar to serous tumors at the molecular level. In analyses of multiple cancers, the classification model may also be applicable to ovarian cancers.