Sentinel lymph node mapping for endometrial cancer improves the detection of metastatic disease to regional lymph nodes

ObjectiveTo compare the incidence of metastatic cancer cells in sentinel lymph nodes (SLN) vs. non-sentinel nodes in patients who had lymphatic mapping for endometrial cancer and to determine the contribution of metastases detected on ultrastaging to the overall nodal metastasis rate.MethodsAll patients who underwent lymphatic mapping for endometrial cancer were reviewed. Cervical injection of blue dye was used in all cases. Sentinel nodes were examined by routine hematoxylin and eosin (H&E), and if negative, by standardized institutional pathology protocol that included additional sections and immunohistochemistry (IHC).ResultsBetween 09/2005 and 03/2010, 266 patients with endometrial cancer underwent lymphatic mapping. Sentinel node identification was successful in 223 (84%) cases. Positive nodes were diagnosed in 32/266 (12%) patients. Of those, 8/266 patients (3%) had the metastasis detected only by additional section or IHC as part of SLN ultrastaging. Excluding the 8 cases with positive SLN on ultrastaging only, 24/801 (2.99%) SLN and 30/2698 (1.11%) non-SLN were positive for metastatic disease (p = 0.0003).ConclusionUsing a cervical injection for mapping, metastatic cells from endometrial cancer are three times as likely to be detected in SLN than in the non-sentinel nodes. This finding strongly supports the concept of lymphatic mapping in endometrial cancer to fine tune the nodal dissection topography. By adding SLN mapping to our current surgical staging procedures we may increase the likelihood of detecting metastatic cancer cells in regional lymph nodes. An additional benefit of incorporating pathologic ultrastaging of SLN is the detection of micrometastasis, which may be the only evidence of extrauterine spread.

Research highlights
► SLN mapping should be added to our current surgical staging procedures.
► Incorporating pathologic ultrastaging of SLN may help detect micrometastasis.