In the study of malignant thymomas, 10 specific immune cell phenotypes were identified, among which 3 (IgD+ CD24− %B cells, CD20 on IgD− CD38dim, and CD16 on CD14+ CD16+ monocytes) exhibited protective effects, whereas 7 [Memory B cells %B cells, CD20− AC, CD3 on CD28+ CD45RA− CD8br, CD28 on CD28+ CD4+ T cells, CCR2 on CD14+ CD16+ monocytes, CD80 on plasmacytoid dendritic cells (pDCs), and CD80 on CD62L+ plasmacytoid dendritic cells] demonstrated significant pro-tumorigenic roles. The gene discussed is SELL; the disease is thymoma.