GFAP and retinoblastoma: To further characterize the newly established, immortalized primary RB tumor cell line T14 (T14_IM), we used a set of markers including fibroblast (α-SMA), glia (GFAP), tumor associated macrophage (CD68), epithelial (pan-cytokeratin) and mesenchymal (vimentin) markers as well as two RB markers (synaptophysin and TFF1) for immunohistochemical stains.