RBP2 and neoplasm: Several studies suggested that among the tissues of origin there are often two different types of NETs that can arise, one the more conventional, slow growing carcinoid and the other a much more aggressive and poorly differentiated tumor.21, 22 Our results suggest that the differences in the behavior of these two tumor types may depend at least in part, on RBP2 subcellular localization: cytoplasmic in well-differentiated tumor cells, and nuclear in poorly differentiated tumor cells.