Two types of ovarian carcinomas are distinguished with respect to morphology, biology, and clinical course, and are designated as Type I and Type II tumors. However, placement of clear cell carcinomas into one of these 2 groups has been problematic as they exhibit morphologic, molecular, and clinical features that do not entirely resemble either Type I or Type II tumors. The present study aimed at better elucidating the clinicopathologic and immunohistochemical features of clear cell carcinomas, in comparison with the 2 main broad categories. To this end, a panel of classic clinicopathologic and immunohistochemical parameters, including estrogen receptor α (ERα), ERβ, progesterone receptor, Ki67, p53, and HER2/neu was evaluated in 71 Type I, 157 Type II, and 21 clear cell carcinomas. Overall, findings from the present study support the idea that ovarian clear cell carcinomas are neither Type I nor Type II carcinomas of the ovary; indeed, results obtained showed that similarities between clear cell carcinomas and Type I were limited to the patient's age, tumor dimension, incidence of lymph node and extranodal metastases, and p53 labeling index, whereas the patient's age and incidence of extranodal metastases were the only parameters comparable with the Type II group. The hormonal receptor profile of clear cell carcinomas was characterized by low expression of nuclear ERα and progesterone receptor, and by almost exclusively nuclear ERβ immunopositivity, features significantly different from both Type I and II tumors. Finally, the percentage of HER2/neu-positive samples in clear cell carcinomas was 10- and 2.5-fold higher than Type I and Type II ovarian tumors, respectively. In conclusion, our study provides insights into clear cell carcinoma that could help in explaining its unique prognostic features, and, eventually, in orienting toward new therapeutic options.