Dual Modality and Site-differentiated Sentinel Node Mapping in Vulvar Cancer

The question of whether sentinel lymph node (SLN) marking depends on the injection site on the vulva warrants further elucidation. This issue emerges in circumstances where, after the surgical excision of a vulvar tumor, a malignancy is identified microscopically, yet lymph node removal was not initially implemented. In such cases, during subsequent surgical operations for lymph node staging, the injection of a tracer near the tumor becomes impossible, as the tumor has already been removed. In order to elucidate this issue, an investigation was conducted into the marking behavior of inguinal SLNs in dual marking with two different tracers and injections at different sites on the vulva in patients with squamous cell vulvar cancer.

Twenty-seven groins of 15 patients with squamous cell carcinoma of the vulva who underwent SLN resection between 2016 and 2022 at the University Hospital of Cologne, Germany, were analyzed in this retrospective cohort study. As part of SLN marking, a mark was made at various points on the vulva using technetium and indocyanine green (ICG).

SLNs could be harvested from all groins. All radioactively labeled SLNs also showed ICG labeling. After removal of the radioactively labeled SLN, no ICG-labeled lymph nodes were detectable intraoperatively. Three groins in two patients had tumor-infiltrated lymph nodes.

All excised SLNs of the patients with squamous cell carcinoma of the vulva successfully demonstrated uptake of both tracers (technetium and indocyanine green), despite being administered at different injection sites. In this study, the stainability of the inguinal SLN was independent of the respective injection site. This is experimental evidence that, when SLN marking is performed after removal of a vulvar tumor, the same lymph nodes will stain as would be the case if marking were performed during tumor removal.