Table 4.

Definitions of the currently used scoring systems (algorithms) for the immunohistochemical assessment of PD-L1 expression in cancer

Scoring algorithm	Interpretation
Tumor Proportion Score (TPS)	The percentage of viable tumor cells showing partial or complete membrane staining relative to all viable tumor cells present in the sample (positive and negative).
Combined Positive Score (CPS)	Number of PD-L1-positive cells (Tumor cells, lymphocytes, and macrophages) divided by the total number of viable tumor cells in the assessed area, multiplied by 100.
Tumor cells (TC) Score	The percentage of PD-L1-positive tumor cells at any intensity.
Immune cells (IC) Score	The proportion of tumor area occupied by PD-L1-positive immune (mononuclear) cells at any intensity.

PD-L1: Programmed cell death ligand 1.