PECAM1 and cancer: By combining FISH and multiplex IHC (Fig. 2 E, a–h), we stained metastatic lesions in MMTV-PyMT lungs for PTN (RNA-FISH), PyMT antigen (cancer cell marker), CD31 (endothelial marker), CD45 (pan-immune cell marker), and podoplanin (fibroblast, lymphatic maker).