Melanomas are characterized by high metastatic potential, with regional lymph node representing the most frequent site of early dissemination in this disease. These regional lymph nodes also represent the primary site for differentiation of natural killer (NK) cells. Although blood-derived NK cells can efficiently lyse melanoma cells isolated from metastatic lymph node (M-LN), there has been no study of the properties of the most disease-relevant NK cells isolated from M-LN in patients with melanoma. Here, we report that M-LN contains 0.5% to 11% of CD56 bright NK cells among CD45 þ hematopoietic cells present and that this cell