Ovarian tumors, or ovarian neoplasms, are tumors arising from the ovary. They can be benign or malignant (ovarian cancer). They consists of mainly solid tissue, while ovarian cysts contain fluid. Clear cell ovarian carcinoma is one of several subtypes of ovarian carcinoma. Clear cell is a subtype of epithelial ovarian cancer in contrast to non-epithelial cancers. According to research, most ovarian cancers start at the epithelial layer which is the lining of the ovary. Within this epithelial group clear cell ovarian carcinoma makes up about 5-10%. Clear cell ovarian carcinoma was recognized as a separate category of ovarian cancer by the World Health Organization in 1973. Its incidence rate differs across various ethnic groups. Reports from the United States show that the highest rates are among Asians with 11.1% versus whites with 4.8% and blacks at 3.1%. These numbers are consistent with the finding that although clear cell carcinomas are rare in Western countries they are much more common in parts of Asia.