Using the s-ErbB-3 as a marker for cancer

A method for the in vitro evaluation of breast cancer comprising measuring in a sample oplasma serum concentration a) s-ErbB-3, b) optionally one or more other cancer markers, c) use the result of step (a) and optionally step (b) in the assessment of cancer Demama, in which an increased concentration of s-ErbB-3 indicates the presence of breast cancer.