Background. Knowledge of the risk factors for lymph node metastasis (LNM) is necessary to treat patients with endometrioid uterine cancer to optimize and further individualize treatment. This study was designed to determine the risk of LNM based on myometrial invasion and tumor grade in endometrioid uterine cancer. Methods. The authors retrospectively reviewed the medical records and pathological findings of 834 patients who underwent surgical staging, including pelvic lymphadenectomy with or without para-aortic lymphadenectomy, for endometrioid uterine cancer from 2002 to 2008 in Korea. Results. Of the 834 patients with endometrioid uterine cancer, 107 (12.8%) patients had LNM. Sixty-one (57%) patients had only pelvic LNM, 39 (36.4%) had pelvic and para-aortic LNM, and 7 (6.6%) had isolated para-aortic LNM. Tumor grade, myometrial invasion, tumor diameter, cervical extension, lymphovascular space invasion, and adnexal involvement were found to be significant predictors of LNM. Of 215 patients with no myometrial invasion and tumor grade I/II, only 1 (0.47%) had LNM. However, in other patients, the risk of LNM was significant and at least >3.5%. Furthermore, the risk of LNM was found to be well correlated with increases in myometrial invasion and tumor grade based on subgroup analyses, when patients with no myometrial invasion and tumor grade I/II were used as a reference group (p <0.0001). Conclusions. Patients with endometrioid uterine cancers with no myometrial invasion and tumor grade I/II might have minimal risk of LNM, whereas others might require complete pelvic and para-aortic lymphadenectomy for surgical staging.
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