Abstract Over the last decade, endometrial cancer (EC) incidence has increased at an average rate of 0.8% each year. Although cancer death rates decreased during this time, EC showed the greatest increase in cancer death among women. Public awareness of EC remains low, and EC research remains underfunded relative to its societal burden. While most women with EC are post-menopausal, up to 30% of cases occur in pre-menopausal women under 50 years of age, with obesity being a major risk factor. More than half of all EC is associated with obesity. Obesity is also a leading risk factor for benign endometrial hyperplasia, which is considered the precursor lesion to EC. Like other cancers, the causes of EC are multifactorial, with obesity and somatic mutations playing causal roles. By 2030, half of all adult women in the U.S. are expected to be classified as obese. Therefore, EC incidence is expected to increase. If detected early, EC can be cured with surgical hysterectomy, but this solution is not ideal for all women. Intentional weight loss can lower endometrial cancer risk in obese women, but certain barriers prevent obese, at-risk women from losing weight or maintaining healthy lifestyles while living in obesogenic environments. There is a critical need to understand the biological mechanisms underlying EC pathogenesis in at-risk obese women. Although EC is thought to arise from a hyperplastic endometrial epithelium, our previous findings suggest that high-fat diet induced obesity affects other cell types within the endometrial microenvironment, including endometrial stroma and immune cells, in the absence of histopathological change. Common EC somatic mutations can also arise in the absence of histopathological change or occur in cases of benign disease. Our overarching hypothesis is that a normal appearing endometrium may accrue cell-context dependent alterations in response to obesity and somatic mutations across a pre-malignant tissue field that are predictive of malignant transformation. This presentation will highlight our recent work on the combined molecular and phenotypic effects of obesity and common EC driver mutations on the endometrial tissue field. The identification of high-value molecular targets across the endometrial pre-malignant field may inform new early detection and prevention strategies for EC. Citation Format: Ronald Chandler. Understanding field carcinogenesis in obesity-related endometrial cancer [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr IA011.