Our previous studies reported that loss of MED23, one subunit of the tail module of the mediator complex, enhances anti‐tumor function of conventional T cells in PyMT transgenic mice, but inhibits anti‐tumor activity of invariant natural killer T (iNKT) cells in B16F10 melanoma lung metastasis mouse model.[19, 20] Here we find loss of MED23 in T cells (Med23−/−) reduces CD103+ T cells within tissues including the lung. This evidence concerns the gene MED23 and neoplasm.