One of the PRL-modulated genes identified, parathyroid hormone-related peptide (PTHrP), was found by fluorescence-based quantitative immunohistochemistry to positively correlate with levels of nuclear localized, tyrosine phosphorylated Stat5 (Nuc-pYStat5) at the protein level in clinical human breast cancer specimens. The gene discussed is PRL; the disease is breast carcinoma.