Using the 96-gene intrinsic gene list, we found that the five STAT1-/- mammary tumors belong to the same cluster 95% of the time after 1,000 re-samplings with an interquartile range (IQR) of 0.9128 to 0.9775 (range = 0.8964 to 1.0), which indicates that the STAT1-/- mammary tumors are molecularly homogeneous. Here, STAT1 is linked to breast cancer.