AHR (aryl hydrocarbon receptor), is best known as the transcription factor regulating the cytochrome P450 genes, but has also been implicated in liver regeneration7,8, as a tumor suppressor8, in embryogenesis and numerous other processes, likely through its role in the regulation of eicosanoid metabolism, which are bioactive lipid mediators9. The gene discussed is AHR; the disease is neoplasm.