Incidence of omental metastasis in uterine serous carcinoma: study protocol for a systematic review and meta-analysis oleh Yu Xu, Yu Cheng, Lin-Lin Zhang, Cui Hu, Fei-Xue Xue, Ya Jia, Qin Zhao-Juan, Du Yi, Zhang Qian-Wen, He Yue-Dong, Zheng Ai