PDCD1 and neoplasm: The evolution of analytical approaches—from quantifying immune cells infiltration density and immune checkpoint expression (e.g., PD-1, PD-L1) (18, 120), to single-cell and spatial transcriptomic mapping that delineates lineage trajectories, functional reprogramming, and intricate cell–cell communication networks (9, 78, 118)—has elevated the focus from “immune cells quantity” to the broader concept of “immune ecology.” These advances have revealed a strong correlation between tumor differentiation status and the dynamic evolution of TIME in thyroid carcinoma (86, 116).