The present invention relates to the diagnosis of breast cancer. It discloses the use of protein cellular retinoic acid binding protein II in the diagnosis of breast cancer. It relates to a method for diagnosis of breast cancer from a liquid sample, derived from an individual by measuring cellular retinoic acid binding protein II in said sample. Measurement of cellular retinoic acid binding protein II can, e.g., be used in the early detection or diagnosis of breast cancer.