INTRODUCTION
Cutaneous melanoma (CM) is a malignant neoplasm arising from melanocytes.1 Even though melanoma accounts for less than 5% of all skin cancers, the majority of skin cancer deaths are due to melanoma.2 CM is the second most diagnosed cancer in individuals aged 15-29 years in the United States3, while it is the tenth most common cause of death in Australia.4 Recently, an equilibrium has been established in the United States with respect to melanoma mortality.5 Despite a steady increase in the incidence of CM worldwide over the last decades, which might also be due to improved early detection, mortality has remained almost constant in the last decades. The status of the regional lymph nodes is regarded as one of the most important prognostic factors besides the information from the primary melanoma. Traditionally, elective lymph node dissection (ELND) was carried out as a diagnostic and therapeutic procedure in malignant melanomas. However, nowadays sentinel lymph node biopsy (SLNB), a minimally invasive procedure, is considered the gold standard to determine the tumor status of regional nodes and staging of patients with subclinical nodal metastases in patients with tumor thickness ≥1 mm or ≥0.8 mm with additional risk factors. The concept of SLNB was introduced by Morton in the early 90s and it is based on the observation that the lymphatic flow follows a constant anatomical route, with the tumor cells directly draining into one or more lymph nodes. By performing an SNLB, the first lymph nodes (or nodes) will be identified.6 SLNB is considered a feasible and reliable procedure in patients with 1-4 mm and >4 mm thick tumors, which has shown metastases in only 20% of cases and lower complication rates than ELND. A meta-analysis of 71 studies estimated the possibility of nodal recurrence after negative SLNB at ≤5% and recurrence at any site at approximately 10%. However, over the last decade, studies have shown an upward trend of falsenegative findings in SLNB, which may lead to wrong prognostic estimates and treatment strategies in these patients.7
Hematoxylin eosin or immunohistochemical (IHC) staining is currently utilized to delineate microscopic nodal metastases
Hematoxylin eosin or immunohistochemical (IHC) staining is currently utilized to delineate microscopic nodal metastases