CD9 and neoplasm: Emerging studies further extend these observations to solid tumors such as renal cell carcinoma (RCC), where tumor cells acquire immune molecules (CD14, CD16, CD56 and CD45) from infiltrating immune-cells (Marcarian et al., 2025), pancreatic ductal adenocarcinoma (PDAC), where cancer-associated fibroblasts transfer cholesterol and plasma membrane lipids to PDAC cells, fostering an immune-suppressive milieu (Ogier et al., 2023) and high-grade serous ovarian carcinoma (HGSC), where trogocytic transfer of CD9 from tumor cells to NK cells hampers their cytotoxicity (Gonzalez et al., 2021).