Immunohistochemical workup of sentinel nodes in endometrial cancer improves diagnostic accuracy.

The purpose of this study was to examine the effect of immunohistochemical (IHC) staining of sentinel (SLN) and non sentinel lymph nodes (NSLN) on the detection of additional metastases in patients with endometrial cancer.Between April 2004 and March 2006, 25 patients with endometrial cancer were operated on. A new method for labelling SLNs with Patent Blue(R) was used. One additional slice was cut out of each lymph node and immunohistochemically stained (IHC). Sentinel and NSLN nodes were re-evaluated.673 lymph nodes from 21 patients were available for re-evaluation. With IHC staining significantly more metastases were detected compared to H&E staining. Though more patients with metastases were discovered this was not significant on the basis of affected SLNs or NSLNs. In the conventional evaluation 7 metastases were found in 3 patients. Applying re-evaluation and IHC 6 additional metastases in 5 patients were detected. These additional metastases were evenly distributed among the pelvic and para-aortic area, and among the SLNs or NSLNs. This had an impact on the diagnostic accuracy of the sentinel concept. Sensitivity reduced from 66.7% to 33.3% and the negative predictive value (NPV) fell from 94.7% to 79.0% only if the NSLNs were additionally IHC stained. On the contrary, if the SLNs were also IHC stained, the sensitivity rose to 83.3%, the NPV rose to 93.8%.Our results indicate that additional immunohistochemistry staining of one additional block of SLNs improves the validity of sensitivity and the NPV in the sentinel concept.