I read with interest the recent case report by Drs Dutt and Berney “Clear cell carcinoma of the ovary arising in a mucinous cystadenoma”.¹ As these authors state, ovarian clear cell carcinomas often arise in endometriosis with a quoted incidence of associated pelvic endometriosis in 50–70% of cases and an incidence of endometriosis in the same ovary of 25%.² This is undoubtedly a gross underestimate of the association between ovarian endometriosis and clear cell carcinoma because in many cases the tumour will overgrow and completely obliterate the endometriosis. However, my personal experience is that when ovarian clear cell carcinomas are extensively sampled (with special reference to cystic areas) the frequency of endometriosis in these neoplasms is substantially higher and indeed the origin of the tumour in an endometriotic cyst can be identified in most cases.

Drs …