October 2005, Vol. 12, No.4

Authors: Christopher A. Puleo, PA-C; Jane L. Messina, MD; Adam I. Riker, MD; L. Frank Glass, MD; Christopher Nelson, MD; C. Wayne Cruse, MD; Timothy M. Johnson, MD; Vernon K. Sondak, MD

Abstract

Background: As the incidence of melanoma increases, thin melanomas are being diagnosed at an increasingly frequent rate. Currently available prognostic factors are limited in their ability to reliably discriminate which patients will manifest regional nodal metastasis and would be identified early through sentinel node biopsy.
Methods: We summarized our experience with sentinel node biopsy for patients with cutaneous melanomas less than 1.00 mm in Breslow thickness, with evaluation of Clark level as a predictor of positive sentinel node metastasis.
Results: Among the 409 patients identified, micrometastases were found in the sentinel node in 20 patients, for an overall incidence of nodal progression of of 4.9%. A total of 252 (62%) were Clark level II or III (11 of whom had a positive sentinel node) and 157 (38%) were Clark level IV (9 of whom had a positive sentinel node). We reviewed the literature to identify reliable indicators that might be helpful in determining which patients with "thin melanomas" would be likely to manifest regional progression to warrant routinely undergoing a preoperative lymphoscintigraphy followed by a sentinel node biopsy.
Conclusions: Based on available data, patients with melanomas between 0.75 and 1.00 mm are appropriate candidates to be considered for sentinel node biopsy after discussing the likelihood of finding evidence of nodal progression, the risks of sentinel node biopsy (including the risk of a false-negative result), and the lack of proven survival benefit from any form of surgical nodal staging.

Introduction

As the incidence of melanoma increases, thin melanomas are being diagnosed at an increasingly frequent rate. In melanoma, progression to the regional nodes is indicative of but not synonymous with decreased disease-free intervals as well as decreased survival. Overall, only approximately half of clinically localized melanomas that have progressed to the regional nodes at the time of diagnosis will ultimately manifest distant metastases, which almost always translates into eventual disease progression. Currently available prognostic factors, which are based on clinical parameters and histologic findings in the primary and metastatic tumor sites, are limited in their ability to reliably discriminate which patients will manifest regional nodal metastasis, making them at high risk for development of disseminated disease.

The widespread use of intraoperative lymphatic mapping and sentinel node biopsy has proven its ability to identify micrometastases in the regional nodes. This then poses the question of the need for all, some, or none of the increasing number of patients with thin melanomas to undergo sentinel node biopsy. Currently, indications for sentinel node biopsy in early-stage melanoma are based primarily on Breslow thickness and the presence of ulceration. The American Joint Committee on Cancer (AJCC) staging system for cutaneous melanoma incorporates Clark level IV or V as a prognostic factor in lesions ≤1.00 mm in Breslow thickness. While Clark level IV or V penetration has been shown to be a significant prognostic factor for overall survival in a large database study, its ability to predict the likelihood of regional nodal progression is less clear. Nonetheless, based primarily on the AJCC staging system, melanomas ≤1.00 mm in Breslow thickness that penetrate into the reticular dermis or subcutaneous fat have been selected for sentinel node biopsy in many centers, while identical thickness lesions with lesser degrees of dermal penetration have not.

In this review article, we summarize our experience with sentinel node biopsy for patients with cutaneous melanomas ≤1.00 mm in Breslow thickness, with particular reference to Clark level as a predictor of progression.