We characterized exosomes from a mouse fibrosarcoma cell line compared with a human breast cancer cell line using DLS, TEM, ExoView, western blot and dot blot, and demonstrated that exosomes from fibrosarcoma contained GM1 ganglioside, HSC70, TSG101, tetraspanins such as CD9, CD81 and CD63, and mainly sized around 50~100 nm in radius. The gene discussed is CD81; the disease is breast cancer.