Only a limited number of comparable investigations exist that analysed the metabolic capacity of human breast tumour tissue such as the both CYP1A1-mediated ethoxyresorufin O-deethylase (Ìscan et al, 1999) and aryl hydrocarbon hydroxylase activities (Pyykko et al, 1991). This evidence concerns the gene CYP3A5 and breast neoplasm.