 Currently, if a patient has a positive or metastatic SN, this patient will be offered a CLND, which is a surgical intervention aiming to remove all lymph nodes from the same nodal basin as the SN. However, if the positive or metastatic SN is only minimally involved, some centers andor countries do not offer a CLND routinely. As a matter of fact, the CLND procedure does not increase survival for patients with a minimal SN tumor burden, but can add prognostic information, potentially useful in the subsequent decision-making process. However, this is a surgical operation for the patient, which might be accompanied by significant side effects. Moreover, only approximately 20 of patients with a metastatic SN have further lymph node metastases in the same basin, which means that about 4 patients out of 5 will not benefit from a CLND. Thus, there is an urgent need to identify which SN positive patients could be safely spared from a CLND. It has been demonstrated that breast cancer patients with minimal SN tumor burden can be safely managed with nodal observation only, without performing a CLND. There is evidence that the same situation exists in melanoma as well, but this needs to be validated and this is why we are conducting this registry. 