Endometriosis is a common gynaecological disease, but malignant transformation of endometriosis is rare. The malignancies arising from ovarian endometriosis are most common, followed by those arising from foci in the pelvic peritoneum and the colorectal tract [
1,
4,
5]. In a systematic review [
6], 80% of all extragonadal endometriosis-associated neoplasms occurred in the rectum and sigmoid colon. Histologically, they were mostly adenocarcinomas. Adenocarcinoma arising from endometriosis often mimics primary intestinal adenocarcinoma. Pathological and immunohistochemical staining are essential to make an accurate clinical diagnosis. The histological diagnosis is based on Sampson’s criteria, which are the basic criteria for the diagnosis of endometriosis-associated malignancy [
7]. Immunohistochemical examinations are also useful to distinguish between adenocarcinoma arising from endometriosis and primary intestinal adenocarcinoma. Endometrioid glands are usually immunoreactive for CK7, and ER, and stromal cells are positive for CD10 and ER. Intestinal glands express CDX2 and CK20, while displaying negative expression of CK7, ER or CD10. PAX8 was shown to be expressed in gynaecological cancers [
8]. To date, there is no consensus on the therapeutic approach to treating endometriosis-associated malignancies. However, surgery with radical resection of the tumour should be performed if possible. The overall effectiveness of chemotherapy is unknown. There has been a broad consensus that the therapeutic principle and regimens applied to ovarian cancer also apply to endometriosis-associated ovarian cancer (EAOC) [
9]. To this end, platinum-taxane combinations should be taken as the first choice for the standard adjuvant therapy [
10]. To date, it is recommended that patients who are diagnosed with extragonadal endometriosis-associated carcinomas, which are confined to the lower pelvic cavity, may benefit from adjuvant pelvic irradiation [
11]. Neoadjuvant preoperative chemotherapy and radiation therapy may be an appropriate additional measure. Considering the rarity of this disease, the application of neoadjuvant therapy must be further investigated. Additionally, the application of endocrine therapy in endometrial carcinoma should be investigated, as hormone-therapy may have a similar efficacy on gestagen receptor-positive endometriosis-associated malignancies. Our report has several limitations. First, we report just one case, and the individual characteristics cannot be generalized to other patients. Second, in the case presented, the patient did not receive adjuvant radiotherapy, which may decrease the local recurrence rate. Lastly, the short follow-up relative to the long-term prognosis must be verified. We will report the long-term follow-up and will pay close attention to similar cases.