CD9 and neoplasm: Additionally, intratumor NK cells differ phenotypically or functionally from peripheral NK cells in several malignancies (Bruno et al., 2013; Carrega et al., 2008); a specific subset of tumor-infiltrating NK cells (CD11b− and CD27−) as well as decidual-like NK (CD9+ and cd49a+) was associated with tumor progression in lung and hepatocellular cancers (Zhang et al., 2017; Jin et al., 2013; Albini and Noonan, 2021).