PD-1 Inhibitor Combined With Progesterone Treatment in FST for Patients With MMRd Endometrial Cancer

Inclusion Criteria: * Be between the ages of 18-45 years old; * Stage IA (FIGO 2009) ; * Confirmed diagnosis of endometrial adenocarcinoma G1-G2 based upon D\&C or hysteroscopy; * Molecular classification of MMRd, determined by immunohistochemical (IHC) for MMR proteins and by the second generation sequencing (NGS) or microsatellite polymerase chain reaction (PCR); * With a strong desire for fertility preservation; * Sign the informed consent. Exclusion Criteria: * Stage IB(FIGO 2009) and above； * Tumour differentiation of G3 or non-endometrioid adenocarcinoma； * Complicated with any other malignancy； * Contraindicated to conservative treatment or the use of pharmaceuticals. * Contraindications to pregnancy, or judged by the researcher to be unfit for pregnancy or delivery.