The incidence of pelvic lymph node metastasis by FIGO staging for patients with adequately surgically staged endometrial adenocarcinoma of endometrioid histology

The seminal Gynecologic Oncology Group study on surgical pathologic spread patterns of endometrial cancer demonstrated the risk of pelvic lymph node metastasis for clinical stage I endometrial cancer based on tumor grade and thirds of myometrial invasion. However, the FIGO staging system assigns surgical stage by categorizing depth of myometrial invasion in halves. The objective of this study was to determine the incidence of pelvic lymph node metastasis in endometrial cancer based on tumor grade and myometrial invasion as per the current FIGO staging system. We reviewed the records of all patients who underwent primary surgical staging for clinical stage I endometrial cancer at our institution between May 1993 and November 2005. To make the study cohort as homogeneous as possible, we included only cases of endometrioid histology. We also included only patients who had adequate staging, which was defined as a total hysterectomy with removal of at least eight pelvic lymph nodes. During the study period, 1036 patients underwent primary surgery for endometrial cancer. The study cohort was composed of the 349 patients who met study inclusion criteria. Distribution of tumor grade was as follows: grade 1, 80 (23%); grade 2, 182 (52%); and grade 3, 87 (25%). Overall, 30 patients (9%) had pelvic lymph node metastasis. The incidence of pelvic lymph node metastasis in relation to tumor grade and depth of myometrial invasion (none, inner half, and outer half) was as follows: grade 1-0%, 0%, and 0%, respectively; grade 2-4%, 10%, and 17%, respectively; and grade 3-0%, 7%, and 28%, respectively. We determined the incidence of pelvic nodal metastasis in a large cohort of endometrial cancer patients of uniform histologic subtype in relation to tumor grade and a one-half myometrial invasion cutoff. These data are more applicable to current surgical practice than the previously described one-third myometrial invasion cutoff results.