We examined associations of circulating IGF-1 and IGF binding protein-3 (IGFBP-3) with expression of CD44, CD24, and ALDH1A1 stem cell markers in benign breast biopsies.<h4>Methods</h4>This study included 151 cancer-free women with incident biopsy-confirmed benign breast disease and blood samples within the Nurses' Health Study II. The gene discussed is CD44; the disease is breast fibrocystic disease.