Impact of Sentinel Node Biopsy on Outcome in Melanoma

The worldwide incidence of malignant melanoma is increasing at an alarming rate. The importance of diagnosing nodal metastatic disease has impacted significantly on the accurate staging and stratification of melanoma patients. As a minimally invasive procedure with low morbidity, sentinel lymph node mapping allows for a detailed histopathologic evaluation involving multiple sections, H&E staining in combination with immunohistochemical staining of the node with the highest chance of containing metastatic foci. Controversy exists regarding the appropriate selection of patients for sentinel lymph node biopsy, particularly among patients with thin melanomas (< 1 mm Breslow thickness), thick melanomas (> 4 mm Breslow thickness), locally recurrent melanoma, nodular melanomas and those affecting the head and neck region. Furthermore, debate continues with regard to false-negative rates, managing in-transit disease, therapeutic benefit and alternatives, such as ultrasound guided biopsy. In malignant melanoma, no standard systemic adjuvant therapy with confirmed impact on overall survival has been identified thus far for clinically node negative stage I-II patients after excision of the primary, or for clinically node positive stage III patients after lymph node dissection for metastatic regional node involvement. Thus some argue about the initial merits of performing the sentinel node procedure at all. The aims of this book chapter are 1. to examine the impact of sentinel node biopsy on outcome in melanoma, 2. determine the effect, if any, of stage migration in melanoma 3. to clarify the impact of the different clinical sites on outcome, 4. to ascertain the reasons behind a lack of universal adoption of sentinel node biopsy in melanoma and 5. to critically assess other emerging strategies in the management of melanoma including frozen section analysis of the sentinel node, imprint cytology of the sentinel node, targeted assessment of the regional lymph node basin, the use of risk stratification algorithms of histological factors of the primary tumour and microRNAs.