PECAM1 and neoplasm: Interestingly, FACS analysis revealed that 1.7%–3.5% of the total tumor cell population was negative for CD45 and/or CD31 respectively (Supplementary Figure S2C), and IHC showed that less than 4% of sporadic tumor cells were epithelial-like and positively stained with Cdh1 (Supplementary Figure S2E), indicating that this tumor was comprised predominantly of lymphoma cells and that a small portion of cells originated from the mammary epithelium.