The relative cell migration of each lymphocyte subset to malignant pleural fluids was comparable to the increment of each subset in MPEs (increment of LAC cells in fold change compared to HF cells: CD20+ B: 1.51(0.57–2.68); CD8+ T: 1.73(0.9–2.69); CD4+ T: 1.31(0.53–2). Here, CD4 is linked to hydrops fetalis.