TFRC and neoplasm: The accumulation of FTS/cyanine NCs in tumor tissues could be attributed to their smaller size (31.0 ± 3.4 nm), which enables their internalization to the tumor sites via the enhanced permeability and retention (EPR) effect, and interference with the intrinsic ability of FTS NCs to gravitate toward physiological cells overexpressing TfR1, such as activated lymphocytes and erythroid precursors, as also observed in previous studies.34, 37