Background: Sentinel lymph node (SLN) biopsy has become the standard of care in malignant melanoma, it is commonly identified by intradermal injection of both radiocolloid tracer and Patent Blue Dye (PBD) around the tumor. This study aims to evaluate the efficacy of PBD in identifying inguinal SLN and also the accuracy of SLN mapping performed by peritumoral injection of PBD without combined radioisotope in malignant melanoma of lower extremity.

Methods: Thirty consecutive patients with primary melanoma of lower exteremity who were referred to Cancer Institute of Tehran University of Medical Science between March 2003 to March 2006 were enrolled in this study. All patients had a preoperative pathologic diagnosis of malignant melanoma, median breslow thickness (range 1-4 mm) and none had clinical or radiologic evidence of nodal involvement or distant metastases.

At surgery PBD was injected around the lesion or scar of excisionl biopsy. Subsequently with a 5cm groin incision SLN Biopsy and complete lymph node dissection was done and all lymph nodes were sent for histopathologic examination. SLN examined by both hematoxylin-eosin and immunohistochemical staining.

Results: SLN identification rate was 100%. No complication directly related to PBD injection was seen. Forty-eight sentinel lymph nodes and 195 non sentinel lymph nodes were harvested. Nineteen SLNS were found to be metastasic in 13 patients (47%). In these patients metastases were found in other inguinal lymph nodes.

In the remaining 17 patients, both the SLN itself and the other removed nodes were negative for the metastatic involvement.

Conclusions: Patent blue dye may be enough to identify superficial inguinal SLN in lower extremity melanoma.