Ovarian Clear Cell Cancer Developing From Endometriosis During Pregnancy

What happened, in summary

A 33-year-old woman was evaluated during pregnancy after ultrasound identified a growing left ovarian mass. She was about 14 weeks pregnant and had originally come for fertility-preservation care. The mass measured about 8.6 by 6.6 by 6.2 cm, and her CA-125 and CA724 levels were elevated. Review of her earlier records showed that a 2 cm cyst had been seen in the same ovary during her first pregnancy 2 years earlier and was thought to be an endometriotic cyst. The lesion had enlarged gradually over those 2 years and then grew more quickly during the current pregnancy. She underwent unilateral salpingo-oophorectomy with pelvic adhesiolysis. During surgery, the enlarged left ovary was adherent to the pelvic wall, while the right adnexa appeared normal. Frozen-section assessment was initially suspicious for a sex cord-stromal tumor, so the definitive diagnosis depended on permanent pathology. Microscopic examination showed ovarian clear cell carcinoma with prominent squamous differentiation. Adjacent tissue contained endometriosis and areas showing a transition from endometriosis to atypical endometriosis and then carcinoma, supporting the evolution of the cancer from the prior endometriotic cyst. Tumor testing included Napsin A positivity and a Ki-67 proliferation index of about 20%.