Objective: We investigated the utility of sentinel lymph node (SLN) mapping for the detection of endometrial carcinoma micrometastases. We reevaluated the accuracy of our SLN detection procedure, this time combining step-serial section with cytokeratin immunostaining.
Patients and methods: Between March 2002 and March 2005, consecutive patients undergoing laparotomy (total abdominal hysterectomy, bilateral salpingo-oophorectomy, total pelvic lymphadenectomy and para-aortic lymphadenectomy to the level of renal veins) with SLN biopsy for endometrial cancer at Tohoku University Hospital were enrolled in this study. Excluded were patients in whom lymph node metastases were detected by routine histological examination or those without detectable SLNs. All surgically removed lymph nodes, including SLNs, were examined histopathologically by immunohistochemistry staining with an anti-cytokeratin antibody (AE1/AE3) combined with step-serial sectioning at 200-500 microm intervals.
Results: Four of seventy-four SLNs (5%) obtained from 20 patients had micrometastases or isolated tumor cells (ITC). In contrast, only 4 of the 1350 non-SLNs obtained from 20 patients (0.3%) had detectable micrometastases. The micrometastases were detected in the external iliac basin (two cases) and in the para-aortic area (two cases). The isolated tumor cell was detected in the external iliac basin (one case).
Conclusion: SLNs detected by our method had micrometastases more frequently than did non-SLNs. Easy detection of micrometastases by immunostaining is only possible with step-serial sectioning of the SLNs.