Objective The aim of this study was to determine the histopathologic characteristics of patients with endometrial carcinoma with low-volume metastases (micrometastases and isolated tumor cells) compared with macrometastases.

Methods We performed a retrospective review of patients with endometrial carcinoma.

Results Among 350 robotic-assisted hysterectomies for endometrial cancer, 187 (53%) underwent attempted sentinel lymph node (SLN) biopsy. At least 1 SLN was detected in 185, a 99% overall detection rate; 108 (58%) also had non-SLNs removed. Among 91 patients with SLNs and non-SLNs from the ipsilateral hemipelvis, both were negative in 74 (81%) and positive in 7 (8%), and 10 (11%) had a positive SLN with negative non-SLNs. Among 17 patients with SLNs and non-SLNs from the contralateral hemipelvis, both were negative in 12 (71%), both were positive in 3 (18%), and 2 patients (12%) had negative SLNs with contralateral positive non-SLNs. Among 79 patients with only a SLN dissection, 4 (5%) were positive; among 69 patients with only a non-SLN dissection, 14 (20%) had positive lymph nodes. Among 24 patients with metastatic SLNs, 9 (38%) had isolated tumor cells, 3 (13%) had micrometastases, and 12 (50%) had macrometastases. Among the 40 total patients with metastatic lymph nodes, low-volume metastases represented the largest metastatic deposit in one third of patients, all of which had SLN dissection. All 12 with low-volume metastases had endometrioid histology compared with less than half (46%) of those with macrometastases (P < 0.01). Grade 1 carcinoma was present in 7 (58%) of the patients with low-volume metastases compared with 4 (14%) of those with macrometastases (P < 0.01) Furthermore, significantly more patients with low-volume metastases versus macrometastases had less than 50% myometrial invasion (67% vs 4%, P < 0.001).

Conclusions Low-volume disease was present in one third of patients with nodal metastases, the largest metastatic deposit only in patients who had SLN dissection; these patients were significantly more likely to have grade 1 endometrioid carcinoma with less than 50% myometrial invasion, traditional “low-risk” features.