To directly examine the singular importance of IL-6 as the activator of Stat3 in breast cancer, pStat3 levels and IL-6 levels were compared by IHC analysis of 82 primary breast cancer specimens and a significant positive correlation was observed between high pStat3 and high IL-6 levels as determined by IHC (p < 0.001). Here, STAT3 is linked to breast carcinoma.