PDCD1 and neoplasm: As TLS development has previously been shown to correlate with clonal dominance in both the CD8+ and CD4+ T-cell compartment and active antitumor immunity (49), we next analyzed the density of CD8+ CTLs as a whole as well as CD8+ CTLs expressing the activation marker PD1 in tumor nests and the surrounding stroma using immunofluorescence microscopy in HGSOC samples (study cohort 1 and 2; Fig. 4A).