CD8A and neoplasm: The commonly used methods including immunohistochemistry, immunofluorescence, flow cytometry, and cytometry by time-of-flight mass spectrometry can only characterize limited types of immune cells based on preselected cellular markers, such as CD8 cells, Treg cells, Th17 cells, and tumor-associated macrophages (TAMs), thus providing limited knowledge of the collective effects of these heterogeneous immune cells [12].