Clear cell carcinoma derived from an endometriosis focus in a scar after a caesarean section--a case report and literature review.

Endometriosis is defined as the occurrence of endometrial glands and endometrial stromal cells outside their typical localization within the uterus. Malignant transformation of endometriosis foci in a scar after a caesarean section (cc) is very rare--until 2013 (in a span of 40 years), about 40 such cases have been described. In our article, we describe a case of a 42-year-old woman with a tumour localized in a scar after a caesarean section. The tumour was diagnosed as clear cell carcinoma derived from an endometriosis focus. The long time interval--17 years in average (from 3 to 39 years) between the surgery (cesarean section in most cases) and the tumor diagnosis is characteristic. In the case we describe, the patient was diagnosed 16 years after the endometriosis focus in the scar had arised. Even though endometriosis is a benign lesion, it has many features distinctive for invasive carcinoma; it may itself undergo a malignant transformation as well as increase the risk of endometrial carcinoma or clear cell ovarian carcinoma. Maybe in future, more exhaustive studies will allow establishing a therapeutic protocol in patients with extra-ovarian malignant transformation of endometriosis foci.