Presacral Clear Cell Carcinoma of Müllerian Origin 20 Years After Hysterectomy and Bilateral Salpingo-Oophorectomy: A Case Report and Literature Review.

Primary presacral clear cell carcinoma (CCC) of Müllerian origin is extremely rare. Malignant transformation of endometriosis is a known phenomenon, though typically involving the ovaries or pelvic peritoneum. Retroperitoneal presentation, especially decades after definitive surgery, is exceedingly uncommon. A 60-year-old woman presented with a large retroperitoneal/presacral pelvic mass leading to hydronephrosis, 20 years after total abdominal hysterectomy and bilateral salpingo-oophorectomy for endometriosis. MRI showed a cystic-solid mass with mural nodularity. Surgical exploration revealed dense retroperitoneal adhesions with involvement of the rectosigmoid and the appendix. En bloc resection was performed in posterior exenterative fashion. Histopathology confirmed clear cell carcinoma arising from endometriotic foci, fulfilling Sampson's criteria. Postoperative management included adjuvant paclitaxel-carboplatin chemotherapy. The patient recovered uneventfully and was scheduled for ileostomy reversal. This case illustrates the potential late malignant transformation of endometriosis into Müllerian CCC even decades after hysterectomy and oophorectomy. Endometriosis-associated carcinoma should be considered in the differential diagnosis of retroperitoneal pelvic masses, particularly in women with prior endometriosis.