Endometriosis-associated endometrioid adenocarcinoma of the fallopian tube synchronized with endometrial adenocarcinoma: A case report

BACKGROUND: Endometriosis is a common gynecological disorder that affects women of reproductive age. It is characterized by a cancer-like invasion of the extra-uterine endometrium and exhibits a strong association with ovarian clear cell cancer and endometrioid cancer. Endometriosis-associated fallopian tube endometrioid adenocarcinoma synchronized with endometrial adenocarcinoma was rarely reported. CASE SUMMARY: A 49-year-old woman was referred to our hospital complaining about abnormal vaginal bleeding for three years following unsatisfactory medication. Intraoperative frozen sections unexpectedly unveiled an endometrioid cancer of the left fallopian tube with superficial invasion surrounded by diffuse endometriosis synchronized with endometrioid endometrial cancer. CONCLUSION: It was difficult to make a differential diagnosis when confronted with incidental findings of fallopian tube cancer lesions synchronized with endometrial cancer. The key differential diagnosis of primary endometriosis-associated endometrioid adenocarcinoma of the fallopian tube from endometrial adenocarcinoma involvement relies on the pathological identification of malignant transformation in fallopian tube endometriosis disease.