CD274 and neoplasm: The main scoring systems to evaluate the expression of PD-L1 are the tumor proportion score (TPS), defined as the proportion of tumor cells staining positive at any intensity with the marker, and the combined positive score (CPSs), which also take into account the positivity of the immune cells closely associated with the tumor, thus being defined as the ratio of total positive tumor and immune cells to the total number of viable tumor cells.