Importantly, although it may seem counterintuitive at first sight, ICOG-EO classification emphasizes the fact that HER and HESR (with reactive eosinophils) can be observed in neoplastic diseases in which the clonal cells (T-cells, Reed-Steinberg cells, carcinomatous cells, mast-cells, etc.)are the main sources of IL-5 and other eosinophilopoietins. The gene discussed is IL5; the disease is neoplasm.