A simple abdominal hysterectomy and bilateral salpingo-oophorectomy procedure is the standard surgery for endometrial cancer; prognostic factors, such as histologic type, grade, myometrial invasion (MI), cervical invasion, adnexal involvement, and vascular space involvement, usually are evaluated by precise histologic examination with permanent section (PS) after the surgery. In addition, lymphadenectomy has long been adopted for endometrial cancer surgery, because patients with positive lymph nodes show decreased 5-year overall survival rates that range from 65-72%. Comprehensive lymphadenectomy has been considered necessary for both accurate staging and for determining whether adjuvant therapy should be administered.

Regarding the therapeutic benefits of lymphadenectomy for patients with endometrial cancer, recent studies have shown that, in patients with an intermediate or high risk, a complete systematic lymphadenectomy in both the pelvic and paraaortic regions demonstrates a survival benefit. However, other recent prospective studies have not shown any evidence of survival benefit for pelvic lymphadenectomy in patients with low-risk, early-stage endometrial cancer. Based on these observations, it is accepted generally that patients with a low risk of lymph node involvement should avoid this procedure because of its adverse effects, such as lymphedema, lymphocysts, and infections.

In clinical practice, patients who are at low risk for lymph node metastasis are considered to be women without any risk factors on either preoperative or intraoperative findings. Previous studies have shown the depth of MI, tumor grade, and the presence of intraperitoneal spread to correlate independently with a high frequency of nodal metastasis. Mariani et al and Kamura et al demonstrated that tumor diameter (TD) is also correlated closely with the risk of nodal metastasis.

Although many approaches have been proposed to avoid lymphadenectomy that is based on the tumor grade and depth of MI on frozen section (FS), there was not always a high correlation between the FS diagnosis and final pathologic results. The significance of the intraoperative FS diagnosis in endometrial cancer therefore, remains to be elucidated. To date, there have not been any reports that have provided detailed information on the impact of TD on FS diagnosis. We hypothesized that TD might be a factor that affects the accuracy of intraoperative FS diagnosis and could be a breakthrough to improve the accuracy of the method.

In previous studies on FS, it was not possible to confirm whether FS diagnosis could safely identify a population that is free from lymph node metastasis, because the lymph nodes were not examined sufficiently. The frequency of lymph node sampling ranged from 27-76%. In the present study, lymph nodes were dissected more frequently than in previous studies. Lymph node dissection was performed in 86% of all patients in the present series, and investigation for the relationship between FS findings and lymph node metastasis was possible.

This is the first study to examine the impact of TD on the reliability of FS diagnosis for depth of invasion, grade, and low-risk prediction. Furthermore, these data were used to identify the true low-risk population that is free from lymph node metastases and can avoid lymphadenectomy.