Abstract: We researched in a series of human breast cancers of different stages the presence and the expression of Atrial Natriuretic Factor (ANF) and Oxytocin (OX), by immunohistochemistry and RT-PCR. We found a reduction of expression of ANF during cancer progression. By contrast, OX resulted lightly expressed by immunohistochemistry and negative at RT-PCR. We hypothesize that ANF could be considered a novel marker to predict breast cancer progression; by contrast, OX expression should be better investigated, to clarify also the putative role of oxytocinases in human breast carcinogenesis.