Ovarian cancer is the leading cause of death among gynecological tumors. Early diagnosis is imperative for improved survival. Both clear cell and endometrioid carcinoma of the ovary are associated with endometriosis. These might coexist with endometriosis; occurrence within an endometrioma is also occasionally encountered. Here, we present a clear cell carcinoma of the ovary arising from a papillary projection within an endometrioma. The patient was on follow-up for 8 months with the presumptive diagnosis of “simple ovarian cyst”. Unfortunately, there was failure to notice both the endometrioid cystic appearance and the papillary structure within the cyst during follow-up evaluations. Hence, clear cell carcinoma of the ovary should be considered in ovarian masses presenting as large endometrioma and intracystic papillary projections especially during premenopausal period.
Keywords: endometrioma, papillary projection, clear cell ovarian cancer