Clear Cell Carcinoma Arising in Vaginal Endometriosis in a Patient 33 Years after Total Hysterectomy and Bilateral Salpingo-oophorectomy: A Case Report

Abstract Introduction/Objective Endometriosis, a common gynecological disorder characterized by ectopic endometrial tissue, is associated with an increased risk of extraovarian malignancies. Vaginal endometriosis is a rare condition, and the occurrence of vaginal malignancies arising from endometriosis is anticipated to be exceedingly rare. Here, we present a rare case of clear cell carcinoma arising in vaginal endometriosis, occurring three decades post-total hysterectomy and bilateral salpingo-oophorectomy. Methods/Case Report A 71-year-old female presented with abnormal Cologuard results, leading to a colonoscopy revealing a mass in the recto-sigmoid colon. She had undergone total hysterectomy and bilateral salpingo- oophorectomy for leiomyoma and endometriosis 33 years prior. Histopathological examination revealed clear cell carcinoma arising in vaginal endometriosis, with tumor extension through the colon wall to the colonic mucosal surface (Figure 1). Notably, the vaginal mucosal surface was negative for tumor. Immunohistochemistry staining demonstrated positivity for Pax8, CK7, AE1/3, racemase, and p16, while negtive for ER, PR, CDX2, CK20, CAIX, SatB2, RCC, WTI, Napsin, and calretinin (Figure 2). The staining for p53 was patchy (wild type, not mutated). Cancer-type relevant biomarkers reveal BRAF mutation (p.D594G), ARID1A mutation (p.M1564fs), PD-L1 mutation (Positive, CPS:80), and PIK3CA mutation (p.H1047L). The histologic and immunohistochemistry findings are consistent with clear cell carcinoma arising in a long-standing area of endometriosis (previous surgery in 1990). Results (if a Case Study enter NA) NA Conclusion Clear cell adenocarcinoma arising from endometriosis is exceptionally rare. Pathologists must consider the possibility of tumors arising from endometriosis when evaluating bowel or mesenteric neoplasms, even decades post-total hysterectomy and bilateral salpingo-oophorectomy. Immunohistochemistry plays a crucial role in the differential diagnosis between carcinoma arising from endometriosis and primary colonic carcinoma. Additionally, Sampson’s criteria are valuable for diagnosing malignant transformations in endometriosis. The identification of specific cancer-type relevant biomarkers, such as BRAF, ARID1A, PD-L1, and PIK3CA mutations, provides additional insights into the molecular characteristics of the tumor, which may have implications for prognosis and treatment selection.