Eosinophils can infiltrate tumour tissue and, in many cases, regulate their progression, such as interacting with tumour cells themselves by synthesising and secreting proteins, such as cytotoxic cationic proteins, including the eosinophil cationic protein (ECP), major basic protein (MBP), eosinophil peroxidise (EPO), granzyme and TNF, which may result in their death [79]. The gene discussed is EPO; the disease is neoplasm.