PDCD1 and neoplasm: These studies have ultimately defined various cellular components and processes associated with therapeutic resistance, metastasis, and overall prognosis.19–26 Researchers have also highlighted the presence of various immune escape mechanisms within the OS TME that are associated with poorer patient outcomes and lack of response to immunotherapy.27 Recently, Ligon et al. characterized the upregulation of immunomodulatory molecules, including programmed death 1 (PD-1), on tumor infiltrating lymphocytes concentrated at the tumor-lung interface of metastatic lesions.