Endometrial cancer (EC) is the most common gynecologic cancer. The most frequent symptom of this disease is postmenopausal bleeding. Diagnosis of EC must be histologically confirmed, and there are several methods for endometrial sampling to obtain cells or endometrial tissue. The first step in diagnosis should be ultrasound measurement of endometrial thickness, followed by endometrial sampling, which can be performed by office endometrial biopsy, hysteroscopic biopsy, or dilatation and curettage (D&C). The review in this article was carried out to present previously published studies, comprehensively evaluate method performance (i.e., overall accuracy of preoperative sampling in patients with endometrial carcinoma, and overall agreement on grade and histological subtype between preoperative endometrial sampling and final diagnosis), and determine which sampling method is most accurate on the basis of the statistical data in the studies analyzed. From the literature analyzed and examined, it can be concluded that preoperative endometrial sampling is not always the best predictor of final histology in EC and has its limitations. In surgical decisions based only on preoperative sampling, a biopsy should be made with caution, and it is necessary to take other parameters into account. Inadequate grading leads to suboptimal clinical management, mainly in early-stage tumors. This review showed that, although hysteroscopic biopsy was mainly associated with the highest tumor grade agreement, and although D&C showed the highest overall accuracy in detecting endometrial carcinoma, the data do not therefore reliably indicate which method yields the most precise results. The results of this review indicate that further studies on larger samples and with greater statistical power are needed to accurately define the role and type of preoperative sampling methods.