A substantial part of estrogen exposure in EC in controlled intracrinally. High mRNA levels of HSD17B1 correlate with poor patient prognosis. Patients with high HSD17B1 and low HSD17B2 mRNA have to poorest prognosis. HSD17B1 is a promising marker to predict EC patient prognosis. Suitable and easy methods to detect HSD17B1 in clinical specimens are needed.