Tumor Microenvironment: Current Understanding and Therapeutic Implications in Adult and Pediatric Cancers

The tumor microenvironment (TME) plays an important role in the development, progression, and treatment response of pediatric cancers, yet remains less elucidated compared to adult malignancies. Pediatric tumors are unique with a low mutational burden, an immature immune landscape, and unique stromal interactions. The resultant “cold” immune microenvironments limits the effectiveness of conventional immunotherapies. This review summarizes the key cellular and non-cellular components of the pediatric TME—including T cells, NK cells, tumor-associated macrophages, cancer-associated fibroblasts, extracellular matrix remodeling, angiogenesis, and hypoxia—and describes how these elements shape tumor behavior and therapy resistance. The role of TME in common pediatric cancers like leukemia, lymphoma, neuroblastoma, brain tumors, renal tumors, and sarcomas is discussed. Emerging therapeutic strategies targeting immune checkpoints, macrophage polarization, angiogenic pathways, and stromal barriers are discussed.