Introduction Aim of the present study was to evaluate the incidence of lymph node metastasis among patients with apparent early stage endometrioid ovarian carcinoma (EOOC).

Methods Patients with apparent early stage EOOC, with known tumor grade and substage diagnosed between 2004–2015 were drawn from the National Cancer Database. Performance of lymph node sampling/dissection (LND) and incidence of LN metastases were evaluated from the pathology report.

Results A total of 9725 patients with apparent early stage EOOC were identified; 44.4%, 40.5% and 15.1% had grade 1, 2 and 3 tumors respectively. 7480 (76.9%) underwent LND with a median of 12.5 LNs removed. The overall incidence of LN metastasis was 2.2%; specifically, 1.2% for grade 1, 2.2% for grade 2, and 5.1% for grade 3 tumors (p<0.001). For patients with apparent stage IA disease, LN metastases were identified in 0.7%, 1.7%, and 4.9% of grade 1, 2, and 3 cases, respectively, p<0.001. For patients with apparent stage IC disease, LN metastases were identified in 2%, 2.6%, and 5.6% for those with grade 1, 2, and 3 cases, respectively. After controlling for substage, patients with grade 2 tumors were nearly twice (OR: 1.78, 95% CI: 1.20, 2.63), and patients with grade 3 tumors were nearly four times (OR: 4.1, 95% CI: 2.74, 6.22) as likely as those with grade 1 tumor to have LN metastases.

Conclusions The incidence of LN metastasis for patients with grade 1 and 2 EOOC is overall low. LND should be considered for patients with grade 3 tumors.