CD8A and neoplasm: The authors also compared the tumor microenvironment characteristics in these two groups and showed that BM were two-fold less infiltrated by T-lymphocytes (CD3+ cells) and three times less infiltrated by cytotoxic T cells (CD8+ cells) when compared to their respective primary tumors (median rates; 15% versus 34% for CD3, and 3% versus 10% for CD8 infiltration respectively) [14].