PDCD1 and neoplasm: Proliferating CD8+ T cells (median 1.17 and 1.75 cells per mm2 in tumor and stroma, respectively, p = 0.011) and PD1+ CD8+ T cells (median 3.68 and 11.56 cells per mm2 in tumor and stroma, respectively, p = 0.0001) were also significantly more abundant in chordoma stroma.