Sentinel lymph node biopsy in patients with primary cutaneous melanoma: study of 455 cases

The role of elective lymph node dissection in the treatment of patients with primary melanoma is a debated topic in surgical oncology. However, recent data assure a survival improvement with this technique only for patients harbouring nodal metastases. The emergence of a new procedure of lymphatic mapping permits the identification of the sentinel lymph node (SLN), the first draining node from the site of cutaneous melanoma, which has demonstrated to be predictive of staging of the entire regional lymphatic basin and useful in selecting for lymph node dissection only those patients who have early micrometastases.

To verify in a large series of cases whether a combination of preoperative lymphoscintigraphy and intraoperative mapping with both vital blue dye and a hand-held gamma probe would permit an increase of the rate of successful SLN localization up to 100%; to check the utility of a wider application of SLN biopsy in patients with thin melanomas owing to a favourable risk-benefit ratio; to determine the predictive value of SLN biopsy by performing regional lymphadenectomy in patients who have pathological evidence of metastases in the SLN; to observe whether the use of SLN technique and selective lymphadenectomy might improve the clinical evolution of patients and favour low rates of recurrence.

In 425 AJCC stage I or II melanoma patients, preoperative lymphoscintigraphy by intracutaneous injection of Tc99m-labelled albumin nanocolloids around the tumour or the tumour's excision scar was combined with the intraoperative use of a hand-held gamma probe and patent blue V mapping technique, in order to identify and harvest the SLN. In five cases the blue dye was voluntarily not used because of previous allergic reactions. In other 25 preliminary cases the procedure was performed using the blue dye alone (10 cases) or combined with a preoperative lymphoscintigraphy (15 cases). A wide excision of the primary site was then undertaken in all cases. SLNs were sent to the pathologist for serial sectioning and permanent preparations with histological and immunohistochemical examination. Patients with pathological evidence of metastatic disease in SLN returned for regional lymphadenectomy.

The combined use of lymphoscintigraphy, blue dye and gamma probe allowed us to identify one or more SLNs in all cases except for two (99.5% rate of success). In 70 melanomas less than 0.76 mm thick, SLNs were negative for metastases, whereas in 380 patients with thicker tumours micrometastases were demonstrated in 75 cases (19.7%). In patients with SLN metastases who underwent regional lymph node dissection, no other metastases were found three times out of four. After a median follow-up period of 18 months the rate of recurrence of the disease in 335 patients with SLN free of metastasis was low (5.4%) with a very low regional nodal recurrence (1.2%). Moreover, the worsening of the disease did not exceed 18.5% of cases with metastasis in SLN.

Our data confirm in a large series of cases that the SLN biopsy is extremely selective and useful to find early micrometastases and to identify patients needing regional lymphadenectomy and adjuvant immunotherapy. Patients with intermediate thickness melanoma (0.76-4.0 mm) should be informed on the availability of such a revolutionary procedure, which represents a new opportunity in primary melanoma surgery.