117 Clear Cell Carcinoma of Müllerian Origin Arising in Abdominal Wall From a Potential Focus of Endometriosis in a Young Patient: Case Report and Review of the Literature

Abstract

Introduction: Carcinoma of Müllerian origin arising from an extrapelvic focus of endometriosis is very rare with few cases reported in the literature. Abdominal skin scar endometriosis is rare (incidence of 0.03%-0.17%) and is usually caused by surgical procedures that displace endometrial tissue into the abdominal wall. Malignant transformation occurs in 0.75% of women with endometriosis, mostly in ovarian foci (80%). Methods: We report a case of clear cell carcinoma arising in a possible endometriosis focus within the abdominal wall using clinical data and gross/microscopic pathologic information. H&E and immunostains were performed. PubMed search was performed using the descriptors “endometriosis” and “clear-cell-carcinoma.” Results: A 26-year-old woman with history of endometriosis and previous cesarean sections, abdominal wall hernia repair, and scar excision presented with a mass in the midline of the abdominal wall. A CT scan showed a multiseptated cystic lesion between the rectus abdominis muscles. The biopsy showed an atypical papillary lesion, weakly positive for CK5/6 and negative for calretinin and CEA. The patient underwent excision of the mass. Gross examination revealed a 9 x 8 x 3.2 cm mixed cystic/solid mass with adjacent posterior peritoneum surface. Microscopic examination showed a mixed papillary/tubulocystic proliferation of atypical cells with cytoplasmic clearing. Immunohistochemically, the lesion was positive for Pax8, BerEP4, Napsin A, and p53, and negative for estrogen receptor, WT1, calretinin, D240, CK20, CDX2, and CEA. Based on the morphology, location and clinical history, these findings are consistent with clear cell carcinoma of Müllerian origin, probably arising from an extra-pelvic focus of endometriosis. Conclusion: Despite being well established in ovarian endometriosis, clear cell carcinoma is rare in endometriosis in other locations. Most malignancies arising from extra-ovarian foci of endometriosis are endometrioid carcinomas (88%). Clear cell carcinomas characteristically have a more aggressive course and worse prognosis.