Abstract
OBJECTIVE: We report the incidence of occult nodal metastasis in patients who underwent primary surgical staging for apparent early endometrioid or serous endometrial cancer with bilateral SLN mapping and enhanced pathology. Occult ovarian metastasis rates were also reported. METHODS: Patients with clinical stage I serous or endometrioid endometrial cancer who underwent primary staging surgery with successful bilateral SLN mapping from 1/2005-12/2018 were retrospectively evaluated. Rates of isolated tumor cells (ITCs), micro- and macrometastatic nodal disease, and occult ovarian involvement were reported. RESULTS: Of 1044 patients, 959 had endometrioid and 85 serous carcinoma. There were no positive SLNs among 510 patients with noninvasive FIGO grade 1/2 endometrioid carcinoma and < 1%ITCs. Grade 1: 4.5%(9/202) with inner-half and 10%(6/62) with outer-half myoinvasion had positive SLNs. Grade 2: rates were 4%(3/76) and 20%(8/41), respectively. Grade 3: 5%(1/20) with noninvasive, 3%(1/31) with inner-half, and 24%(4/17) with outer-half myoinvasion had positive SLNs. ITC incidence increased with depth of myoinvasion-25% of deeply invasive grade 1/2 and 18% of deeply invasive grade 3 tumors. Four (10%) of 41 patients with noninvasive serous endometrial carcinoma had ITCs or positive SLNs. There were no occult ovarian metastases with grades 1/2 disease, 2/68 (3%) with grade 3 disease, and 2/85 (2%) with serous endometrial carcinoma. CONCLUSION: Ultrastaging SLNs may be unwarranted in low-grade noninvasive endometrioid cancer but valuable in noninvasive serous carcinoma. Occult ovarian metastasis is uncommon in early endometrial carcinoma and occurs in 2-3% of high-risk histologies. Further research is needed to determine ITC significance, particularly with regard to adjuvant treatment.