Clear-cell carcinoma of the endometrium:type I or type II endometrial carcinoma?

Purpose of Investigation: To determine if clear cell carcinoma (CCC) should be classified as a type I or type II carcinoma and provide guidance for clinical treatment. Material and Methods: This study included three groups of endometrial carcinomas: 92 cases of CCC were collected from 22 hospitals in China from January 2003 to November 2014, 272 cases of EMA were collected from Peking University People's Hospital from February 2003 and July 2016, and 192 cases of USC were collected from 22 hospitals in China from February 2001 to December 2014. The 2009 FIGO staging system was used and information concerning clinicopathological features was collected. Results: The mean age in the CCC and USC groups was higher than that of the EMA group (p < 0.001). There was no significant difference in the FIGO Stage between the CCC and EMA groups (p = 0.158). There was no significant difference in the extent of myometrial invasion between the three groups (p = 0.064), but there was a significant difference in cervical involvement, adnexal metastasis, and lymph node metastasis (p = 0.017, p < 0.001, and p < 0.001). The patients in the CCC, EMA, and USC groups were followed up for an average of 105.6 +/- 7.5 months, 135.0 +/- 2.2 months, and 92.1 +/- 4.4 months, respectively. Fourteen cases with CCC recurred, and 13 ended in death. There was no significant difference between the CCC and the EMA groups in recurrence and death rates (p = 0.035 > 0.0167, p = 0.018 > 0.0167, 0.0167 = 0.05/3), but the prognosis in the USC group was worse. Conclusions: CCC may follow an overlapping or a third pathway of carcinogenesis, rather than belong to the type II carcinogenesis. Therefore, if CCC should be classified as a type I or type II carcinoma is yet to be determined. Additional studies of the clinicopathological features underlying CCC will facilitate more elective management and avoid unnecessary or non-elective treatments.