Clear Cell Carcinoma Arising from Endometriosis in a C-section Scar: A Case Report with Literature Review

Abstract

Endometriosis is a frequent benign disorder. Malignancy arising in association with endometriosis mainly includes endometrioid carcinoma (70%), sarcoma (25%) and clear cell carcinoma (5%). The incidence rate of abdominal surgical scar endometriosis is between 0.03% and 1.08% of women undergoing pelvic surgery. Malignant transformation arising on the background of scar endometriosis is extremely rare.

Here, we report a case of clear cell carcinoma arising from endometriosis in a cesarean section scar in a 48-year-old woman. The patient presented to the emergency department with a palpable abdominal mass and constipation. A CT scan revealed a mass in the infraumbilical suprapubic rectus abdominis muscle region at the site of a cesarean section scar. A biopsy of this mass revealed an epithelioid neoplasm with papillary features, which is positive for AE1/AE3, PAX-8, and Napsin, suspicious for malignancy of gynecologic or upper urinary tract origin. The patient underwent an exploratory laparotomy, abdominal wall resection and reconstruction, and total abdominal hysterectomy with bilateral salpingo-oophorectomy. The resulting specimen included a 13.7 x 10.0 x 7.0 cm portion of red-yellow muscle and adipose tissue from the abdominal wall. Microscopic examination showed clear cell carcinoma arising from endometriosis in a cesarean section scar. ER, PR, and FOLR1 are all negative, compatible with the diagnosis. There was also metastasis to 6 out of 14 total lymph nodes submitted. The omentum, appendix, uterus, ovaries, fallopian tubes, and cervix were all benign, with the uterus containing a disordered and proliferative endometrium.

Although clear cell carcinoma arising from malignant transformation of endometriosis in the abdominal wall after cesarean section is extremely rare, for a female patient with a history of gynecologic or obstetric surgery, developing an abdominal wall mass, the possibility of a primary malignancy arising from endometriosis should be considered in the differential diagnosis. A tissue biopsy with histological evaluation and ancillary studies should be performed to ensure early detection of malignancy with proper next step treatment.
[N A J Med Sci. 2025;18(1):018-020.   DOI:  10.7156/najms.2025.1801018]

Key Words: Endometriosis, Malignant Transformation, Clear Cell Carcinoma, Abdominal Wall Scar