This study reports a rare case of endometriosis-associated intestinal tumor (EAIT) in a 53-year-old woman who presented with rectal bleeding. Imaging and histopathology confirmed endometrioid adenocarcinoma arising from rectal endometriosis with ovarian metastasis. The patient underwent posterior total pelvic exenteration followed by adjuvant chemotherapy and has remained disease-free for 3.5 years. Comprehensive proteomic profiling of the tumor identified 9,294 proteins, with data deposited in the jPOST repository. This case highlights the diagnostic challenges, clinical management strategies, and biological insights of EAIT, providing a valuable reference for future comparative and translational research.