Study Goal: This pilot study wants to find out if using a menstrual cup can be a good, non-invasive way to collect samples from the lining of the uterus (called the endometrium) to help screen for endometrial cancer. This is especially important for women who have a higher chance of getting this cancer, such as those with a genetic condition called Lynch syndrome. Main Questions the Study Will Answer: 1. Can a menstrual cup collect enough uterine lining (endometrial tissue) for doctors to examine under a microscope? 2. Are the samples from the menstrual cup as useful for diagnosis as samples taken using the usual method (called an endometrial biopsy or EMB)? 3. Is using a menstrual cup at home easy, effective, and comfortable for participants? 4. Can scientists grow small lab models of the uterus (called organoids) from the menstrual cup samples and from biopsy samples? What Will Happen in the Study: * Participants will use a menstrual cup at home to collect menstrual blood. * They will also have a standard endometrial biopsy done by a healthcare provider. * After both collections, participants will fill out a short survey about how comfortable and easy it was to use the menstrual cup. What the Study Will Measure: * Feasibility: How well participants are able to use the menstrual cup and send in the sample. * Sample Quality: Whether the menstrual cup collects enough good-quality tissue for testing, and how it compares to biopsy samples. * Participant Experience: How women feel about using the menstrual cup, based on the survey. * Lab Testing: Whether researchers can successfully grow endometrial organoids from both types of samples. Why This Study Matters: If this method works, it could offer a gentler, more convenient way for women to get checked for endometrial cancer-especially those who need regular screening. It could also make it easier to collect samples for research and improve early detection of cancer.