This article reports a case of rectal-Sigmoid colon clear cell carcinoma with endometrial adeno⁃carcinoma based on endometriosis and analyzes its features and treatment. The female patient

aged 66 years

attend⁃ed our hospital with the chief complaint of abdominal distension for 10 days

and clinical manifestation included a mass in the right lower abdomen

with no obvious tenderness or abnormalities in anal examination. Imaging examina⁃tion showed an irregular soft tissue mass on the right side of the pelvic cavity

located at the right side of the sigmoid colon

with unclear boundaries between the left side of the lesion and the sigmoid colon

which led to the eccentric stenosis of the intestinal cavity

and irregular masses were observed above the vaginal stump

with unclear boundar⁃ies between the lesion and the intestinal canal. The patient underwent total hysterectomy+right adnexectomy+left ovarian cyst removal due to ovarian endometriosis at both sides 20 years ago. The masses in the rectum

the sigmoid colon

and the right iliac fossa were surgically removed

and pathological examination showed endometrial adenocar⁃cinoma with clear cell carcinoma. Lipusu 240 mg and carboplatin 500 mg were given as postoperative chemotherapy. Recurrence and progressive enlargement of tumor were observed during chemotherapy

with continuous increases in tumor markers

and progression was still observed after the drug was switched to Domesil 50 mg. The case of endome⁃triosis involving the intestine with malignant transformation is rare

and this case is resistant to chemotherapy. Fur⁃ther studies are needed to explore the promotion of the same treatment method as ovarian cancer.