This is a case report of a 56-year-old woman with a history of postmenopausal bleeding, who presented with an endometrioid adenocarcinoma and a co-existing non-gestational choriocarcinoma. We performed robotic assisted hysterectomy, bilateral oophorectomy and pelvic lymphadectomy, and histopathologic examination revealed a malignant tumour showing an endometrioid adenocarcinoma grade 2 with a minor component of choriocarcinoma incorporated into the adenocarcinoma. We compared data from exome sequencing of DNA from tumour and blood to show, that the choriocarcinoma component was most likely non-gestational.