Sentinel lymph node identification with technetium-99m-labeled nanocolloid in squamous cell cancer of the vulva

In patients with early-stage squamous cell cancer of the vulva, inguinofemoral lymphadenectomy is performed primarily as a diagnostic procedure. The morbidity of this procedure, however, is not negligible. The aim of this study was to evaluate the feasibility of minimally invasive detection of the sentinel inguinofemoral lymph node (SILN) and to investigate whether the histopathology of the SILNs is representative of that of the other non-SILNs.

Patients with early-stage squamous cell cancer of the vulva, planned for resection of the primary tumor and uni- or bilateral inguinofemoral lymphadenectomy, were eligible for the study. Technetium-99m-labeled nanocolloid was injected intradermally at four locations around the tumor the day before operation. Images were recorded immediately and after 2.5 hr using a gamma camera. SILN locations were marked on the overlying groin skin. The next day, during general anesthesia, blue patent dye was injected intradermally at the same locations around the tumor. During the operation SILNs were identified at the place indicated using a handheld gamma-detection probe. It was noted if SILNs were found by the probe, by blue dye or by both techniques. After resection of the SILNs, a standard inguinofemoral lymphadenectomy was performed. The results of histopathology of the SILNs were compared with those of the non-SILNs.

The procedure was well tolerated by 10 of 11 patients. One patient, initially agreeing to participate, refused the injection of tracer because of fear of pain. In all 10 patients, identification of the SILNs was successful. The mean time for identification was 11 min. Identification of SILNs was primarily performed using the hand probe in all patients, whereas in 10 of 18 removed SILNs afferent lymph channels were also blue stained (56%). In 8 patients, pathologic examination showed no metastatic disease in both SILNs and non-SILNs, whereas in 2 patients metastases in the SILNs (one and two metastatic lymph nodes, respectively), as well as in other non-SILNs, were found.

This study shows that identification of SILNs in squamous cell cancer of the vulva is feasible with preoperatively administered 99mTc-labeled nanocolloid. Intraoperatively administered blue dye was only useful for confirmation of identification with nanocolloid. To date, no false-negative SILNs have been found, but expansion of the study is necessary to determine the possible clinical application of this new diagnostic technique.