35. Clear cell carcinoma arising within an endometrioma

Abstract

There is an increasing awareness that malignant transformation of endometriosis is an uncommon but distinct entity. We review one such case of a clear cell carcinoma arising within an endometrioma of a rectus sheath scar. These malignancies have a favourable prognosis, with extra-gonadal disease commonly associated with unopposed estrogen replacement therapy. Presentation A 56-year-old female presented to TQEH for management of post menopausal bleeding. She proceeded to undergo a hysterectomy and bilateral salpingo-oopgerectomy. She underwent a simultaneous excision of an endometrioma arising in a rectus sheath scar in the setting of previous endometritis. Her previous medical history is otherwise unremarkable with no other recorded malignancies or family history of endometrial adenocarcinoma. Findings 5-10% of the endometrium showed complex endometrial hyperplasia with secretory change. There was also a background of early mid-secretory change with corpus luteum formation in the right ovary. There were five intramural and subserosal leiomyomas (5-80mm in diameter) with no evidence of ovarian endometriosis. A single focus of cervical endometriosis was identified. Sectioning through the endometrioma from the rectus sheath showed a clear cell carcinoma arising in the setting of endometriosis. The tumour was ER negative, CK 7 positive, CK 20 negative and CDX2 negative. It measured 12 mm maximally with the closest soft tissue margin 3-4 mm. No origin from the ovaries or endometrium was identified. Conclusion Carcinoma arising in extra-ovarian foci of endometriosis is a rare but recognised phenomenon. Most of these tumours are either endometrioid or clear cell, as in this case. Radiation and/or chemotherapy is offered with favourable prognosis.